Electrical Surgical Instrument with Optimal Tissue Compression

ABSTRACT

A surgical instrument comprising a tissue-compressing device comprising opposing compression surfaces, a switching element having first and second switching states changed solely by mechanical movements, a biasing element mechanically coupled to the switching element, the biasing element retaining the switching element in one of the first and second switching states until a pre-determined force is imparted to the switching element, wherein the pre-determined force is an amount of force proportional to an optimal tissue compression force of compressed tissue disposed between the opposing compression surfaces and the switching element is positioned in line with the tissue-compressing device to cause a force, proportional to a force placed upon compressed tissue disposed between the opposing compression surfaces, to be imparted to the switching element.

CROSS-REFERENCE TO RELATED APPLICATION

This application is:

-   -   a divisional of U.S. patent application Ser. No. 11/705,381, now        U.S. Pat. No. 8,038,046, filed on Feb. 12, 2007 (which        application claims the priority, under 35 U.S.C. §119, of U.S.        Provisional Patent Application Ser. Nos. 60/801,989, filed on        May 19, 2006, 60/810,272, filed on Jun. 2, 2006, and 60/858,112,        filed on Nov. 9, 2006);    -   a divisional of U.S. patent application Ser. No. 11/705,246, now        U.S. Pat. No. 8,028,885, filed on Feb. 12, 2007 (which        application claims the priority, under 35 U.S.C. §119, of U.S.        Provisional Patent Application Ser. Nos. 60/801,989, filed on        May 19, 2006, 60/810,272, filed on Jun. 2, 2006, and 60/858,112,        filed on Nov. 9, 2006);    -   a divisional of U.S. patent application Ser. No. 11/705,334, now        U.S. Pat. No. 8,573,462, filed on Feb. 12, 2007 (which        application claims the priority, under 35 U.S.C. §119, of U.S.        Provisional Patent Application Ser. Nos. 60/801,989, filed on        May 19, 2006, 60/810,272, filed on Jun. 2, 2006, and 60/858,112,        filed on Nov. 9, 2006);    -   is a continuation-in-part of U.S. patent application Ser. No.        11/750,622, filed May 18, 2007, now U.S. Pat. No. 7,479,608        (which claims the priority, under 35 U.S.C. §119, of U.S.        Provisional Patent Application Ser. No. 60/801,989, filed on May        19, 2006);    -   a divisional of U.S. patent application Ser. Nos. 12/102,181 and        12/102,464 filed on Apr. 14, 2008, (which applications claim        priority, under 35 U.S.C. §119, of U.S. Provisional Patent        Application Ser. No. 60/997,489, filed Oct. 4, 2007);    -   is a continuation-in-part of U.S. patent application Ser. No.        12/270,518, filed Nov. 13, 2008;    -   a divisional of U.S. patent application Ser. No. 12/612,525        filed on Nov. 4, 2009;    -   is a continuation-in-part of U.S. patent application Ser. No.        12/728,471, filed Mar. 22, 2010;    -   a divisional of U.S. patent application Ser. No. 12/793,962,        filed on Jun. 4, 2010;    -   a divisional of U.S. patent application Ser. No. 13/229,076,        filed on Sep. 9, 2011;    -   is a continuation-in-part of U.S. patent application Ser. No.        13/571,159, filed Aug. 9, 2012;    -   a divisional of U.S. patent application Ser. No. 13/611,881,        filed on Sep. 12, 2012;    -   a divisional of U.S. patent application Ser. No. 13/622,819,        filed on Sep. 19, 2012;    -   a divisional of U.S. patent application Ser. No. 13/743,179        filed on Jan. 16, 2013;    -   a divisional of U.S. patent application Ser. No. 13/798,369,        filed on Mar. 13, 2013;    -   is a divisional of U.S. patent application Ser. No. 13/847,971,        filed Mar. 20, 2013;    -   is a divisional of U.S. patent application Ser. No. 13/863,978,        filed Apr. 16, 2013;    -   a divisional of U.S. patent application Ser. No. 13/889,931,        filed on May 8, 2013; and    -   is a continuation-in-part of U.S. patent application Ser. No.        14/036,630, filed Sep. 25, 2013, the entire disclosures of these        applications are all hereby incorporated herein by reference in        their entireties.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

N/A

FIELD OF THE INVENTION

The present invention lies in the field of surgical instruments, inparticular but not necessarily, stapling devices. The stapling devicedescribed in the present application is a hand-held, fully electricallypowered and controlled surgical stapler.

BACKGROUND OF THE INVENTION

Medical stapling devices exist in the art. Ethicon Endo-Surgery, Inc. (aJohnson & Johnson company; hereinafter “Ethicon”) manufactures and sellssuch stapling devices. Circular stapling devices manufactured by Ethiconare referred to under the trade names PROXIMATE® PPH, CDH, and ILS andlinear staplers are manufactured by Ethicon under the trade namesCONTOUR and PROXIMATE. In each of these exemplary surgical staplers,tissue is compressed between a staple cartridge and an anvil and, whenthe staples are ejected, the compressed tissue is also cut. Dependingupon the particular tissue engaged by the physician, the tissue can becompressed too little (where blood color is still visibly present in thetissue), too much (where tissue is crushed), or correctly (where theliquid is removed from the tissue, referred to as desiccating orblanching).

Staples to be delivered have a given length and the cartridge and anvilneed to be within an acceptable staple firing distance so that thestaples close properly upon firing. Therefore, these staplers havedevices indicating the relative distance between the two planes andwhether or not this distance is within the staple length firing range.Such an indicator is mechanical and takes the form of a sliding barbehind a window having indicated thereon a safe staple-firing range.These staplers are all hand-powered, in other words, they requirephysical actuations by the user/physician to position the anvil andstapler cartridge about the tissue to be stapled and/or cut, to closethe anvil and stapler cartridge with respect to one another, and to fireand secure the staples at the tissue (and/or cut the tissue). No priorart staplers are electrically powered to carry out each of theseoperations because the longitudinal force necessary to effect staplefiring is typically on the order of 250 pounds at the staple cartridge.Further, such staplers do not have any kind of active compressionindicator that would optimizes the force acting upon the tissue that isto be stapled so that tissue degradation does not occur.

One hand-powered, intraluminal anastomotic circular stapler is depicted,for example, in U.S. Pat. No. 5,104,025 to Main et al., and assigned toEthicon. Main et al. is hereby incorporated herein by reference in itsentirety. As can be seen most clearly in the exploded view of FIG. 7 inMain et al., a trocar shaft 22 has a distal indentation 21, somerecesses 28 for aligning the trocar shaft 22 to serrations 29 in theanvil and, thereby, align the staples with the anvils 34. A trocar tip26 is capable of puncturing through tissue when pressure is appliedthereto. FIGS. 3 to 6 in Main et al. show how the circular stapler 10functions to join two pieces of tissue together. As the anvil 30 ismoved closer to the head 20, interposed tissue is compressedtherebetween, as particularly shown in FIGS. 5 and 6. If this tissue isovercompressed, the surgical stapling procedure might not succeed. Thus,it is desirable to not exceed the maximum acceptable tissue compressionforce. The interposed tissue can be subject to a range of acceptablecompressing force during surgery. This range is known and referred to asoptimal tissue compression or OTC, and is dependent upon the type oftissue being stapled. While the stapler shown in Main et al. does have abar indicator that displays to the user a safe staple-firing distancebetween the anvil and the staple cartridge, it cannot indicate to theuser any level of compressive force being imparted upon the tissue priorto stapling. It would be desirable to provide such an indication so thatover-compression of the tissue can be avoided.

SUMMARY OF THE INVENTION

The invention overcomes the above-noted and other deficiencies of theprior art by providing an electric surgical stapling device that iselectrically powered to position the anvil and stapler cartridge withrespect to one another about the tissue to be stapled and/or cut, toclose the anvil and stapler cartridge with respect to one another, andto fire and secure the staples at the tissue (and/or cut the tissue).Further, the electric surgical stapling device can indicate to the usera user-pre-defined level of compressive force being imparted upon thetissue prior to firing the staples. The present invention also providesmethods for operating the electric surgical stapling device to staplewhen OTC exists.

An offset-axis configuration for the two anvil and staple firingsub-assemblies creates a device that can be sized to comfortably fitinto a user's hand. It also decreases manufacturing difficulty byremoving previously required nested (co-axial) hollow shafts. With theaxis of the anvil sub-assembly being offset from the staple firingsub-assembly, the length of the threaded rod for extending andretracting the anvil can be decreased by approximately two inches,thereby saving in manufacturing cost and generating a shorterlongitudinal profile.

An exemplary method for using the electric stapler includes a power-onfeature that permits entry into a manual mode for testing purposes. In asurgical procedure, the stapler is a one-way device. In the test mode,however, the user has the ability to move the trocar back and forth asdesired. This test mode can be disengaged and the stapler reset to theuse mode for packaging and shipment. For packaging, it is desirable (butnot necessary) to have the anvil be at a distance from the staplecartridge. Therefore, a homing sequence can be programmed to place theanvil 1 cm (for example) away from the staple cartridge before poweringdown for packaging and shipment. Before use, the trocar is extended andthe anvil is removed. If the stapler is being used to dissect a colon,for example, the trocar is retracted back into the handle and the handleis inserted trans-anally into the colon to downstream side of thedissection while the anvil is inserted through a laparoscopic incisionto an upstream side of the dissection. The anvil is attached to thetrocar and the two parts are retracted towards the handle until a stapleready condition occurs. The staple firing sequence is started, which canbe aborted, to staple the dissection and simultaneously cut tissue atthe center of the dissection to clear an opening in the middle of thecircular ring of staples. The staple firing sequence includes an optimaltissue compression (OTC) measurement and feedback control mechanism thatcauses staples to be fired only when the compression is in a desiredpressure range, referred to as the OTC range. This range or value isknown beforehand based upon known characteristics of the tissue to becompressed between the anvil and staple cartridge.

Some exemplary procedures in which the electric stapler can be usedinclude colon dissection and gastric bypass surgeries. There are manyother uses for the electric stapler in various different technologyareas.

With the foregoing and other objects in view, there is provided, inaccordance with the invention, a surgical instrument comprising atissue-compressing device comprising opposing compression surfaces, aswitching element having first and second switching states changedsolely by mechanical movements, a biasing element mechanically coupledto the switching element, the biasing element retaining the switchingelement in one of the first and second switching states until apre-determined force is imparted to the switching element, wherein thepre-determined force is an amount of force proportional to an optimaltissue compression force of compressed tissue disposed between theopposing compression surfaces and the switching element is positioned inline with the tissue-compressing device to cause a force, proportionalto a force placed upon compressed tissue disposed between the opposingcompression surfaces, to be imparted to the switching element.

In accordance with another mode of the invention, the switching elementis a mechanical binary-output electrical switch.

In accordance with a further mode of the invention, the first switchingstate is an open electrical state and the second switching state is aclosed electrical state.

In accordance with an added mode of the invention, the biasing elementis adjustable.

In accordance with an additional mode of the invention, thepre-determined force of the biasing element is set to an amountproportional to the optimal tissue compression force of the compressedtissue.

In accordance with yet another mode of the invention, the switchingelement is positioned to cause substantially the same force placed uponthe compressed tissue disposed between the opposing compression surfacesto be placed upon the switching element.

In accordance with yet a further mode of the invention, setting thepre-determined force to an amount proportional to the optimal tissuecompression force of the compressed tissue causes a change of theswitching state to occur when a compression force placed on tissue bythe opposing compression surfaces of the tissue-compressing device is atleast as great as the optimal tissue compression force.

In accordance with yet an added mode of the invention, thetissue-compressing device has a compression axis and the switchingelement comprises an actuation gap oriented to span along thecompression axis to cause a change of the switching state dependent upona force expanding along the compression axis.

In accordance with yet an additional mode of the invention, thetissue-compressing device comprises an end effector with two opposingjaws that compress tissue disposed therebetween.

With the foregoing and other objects in view, there is also provided, inaccordance with the invention, a surgical instrument comprising atissue-compressing device comprising opposing compression surfaces, aswitching element having first and second switching states changedsolely by mechanical movements, a biasing element mechanically coupledto the switching element, the biasing element imparting a pre-determinedforce on the switching element to retain the switching element in one ofthe first and second switching states until a switching force at leastas great as the pre-determined force imposed by the biasing element isimparted to the switching element and causes a change of the switchingstate to occur, wherein the pre-determined force is an amount of forceproportional to an optimal tissue compression force of the compressedtissue disposed between the opposing compression surfaces and theswitching element is positioned in line with the tissue-compressingdevice to cause the switching force, proportional to the force placedupon compressed tissue disposed between the opposing compressionsurfaces, to be imparted to the switching element.

Other features that are considered as characteristic for the inventionare set forth in the appended claims. [0022]

Although the invention is illustrated and described herein as embodiedin an electrical surgical instrument with optimal tissue compression, itis, nevertheless, not intended to be limited to the details shownbecause various modifications and structural changes may be made thereinwithout departing from the spirit of the invention and within the scopeand range of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof, will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of embodiments of the present invention will be apparent fromthe following detailed description of the preferred embodiments thereof,which description should be considered in conjunction with theaccompanying drawings in which:

FIG. 1 is a perspective view from a side of an exemplary embodiment ofan electric stapler according to the invention;

FIG. 2 is a fragmentary side elevational view of the stapler of FIG. 1with a right half of a handle body and with a proximal backbone plateremoved;

FIG. 3 is an exploded, perspective view of an anvil control assembly ofthe stapler of FIG. 1;

FIG. 4 is an enlarged, fragmentary, exploded, perspective view of theanvil control assembly of FIG. 3;

FIG. 5 is a fragmentary, perspective view of a staple firing controlassembly of the stapler of FIG. 1 from a rear side thereof;

FIG. 6 is an exploded, perspective view of the staple firing controlassembly of the stapler of FIG. 1;

FIG. 7 is an enlarged, fragmentary, exploded, perspective view of thestaple firing control assembly of FIG. 6;

FIG. 8 is a fragmentary, horizontally cross-sectional view of the anvilcontrol assembly from below the handle body portion of the stapler ofFIG. 1;

FIG. 9 is a fragmentary, enlarged, horizontally cross-sectional viewfrom below a proximal portion of the anvil control assembly FIG. 8;

FIG. 10 is a fragmentary, enlarged, horizontally cross-sectional viewfrom below an intermediate portion of the anvil control assembly of FIG.8;

FIG. 11 is a fragmentary, enlarged, horizontally cross-sectional viewfrom below a distal portion of the anvil control assembly of FIG. 8;

FIG. 12 is a fragmentary, vertically cross-sectional view from a rightside of a handle body portion of the stapler of FIG. 1;

FIG. 13 is a fragmentary, enlarged, vertically cross-sectional view fromthe right side of a proximal handle body portion of the stapler of FIG.12;

FIG. 14 is a fragmentary, enlarged, vertically cross-sectional view fromthe right side of an intermediate handle body portion of the stapler ofFIG. 12;

FIG. 15 is a fragmentary, further enlarged, vertically cross-sectionalview from the right side of the intermediate handle body portion of thestapler of FIG. 14;

FIG. 16 is a fragmentary, enlarged, vertically cross-sectional view fromthe right side of a distal handle body portion of the stapler of FIG.12;

FIG. 17 is a perspective view of a portion of an anvil of the stapler ofFIG. 1;

FIG. 18 is a fragmentary, cross-sectional view of a removable staplingassembly including the anvil, a stapler cartridge, a force switch, and aremovable cartridge connecting assembly of the stapler of FIG. 1;

FIG. 19 is a fragmentary, horizontally cross-sectional view of the anvilcontrol assembly from above the handle body portion of the stapler ofFIG. 1 with the anvil rod in a fully extended position;

FIG. 20 is a fragmentary, side elevational view of the handle bodyportion of the stapler of FIG. 1 from a left side of the handle bodyportion with the left handle body and the circuit board removed and withthe anvil rod in a fully extended position;

FIG. 21 is a fragmentary, side elevational view of the handle bodyportion of the stapler of FIG. 20 with the anvil rod in a 1-cm anvilclosure position;

FIG. 22 is a fragmentary, horizontally cross-sectional view of the anvilcontrol assembly from above the handle body portion of the stapler ofFIG. 1 with the anvil rod in a safe staple firing position;

FIG. 23 is a fragmentary, horizontally cross-sectional view of the anvilcontrol assembly from above the handle body portion of the stapler ofFIG. 1 with the anvil rod in a fully retracted position;

FIG. 24 is a fragmentary, horizontally cross-sectional view of thefiring control assembly from above the handle body portion of thestapler of FIG. 1;

FIG. 25 is a fragmentary, enlarged, horizontally cross-sectional viewfrom above a proximal portion of the firing control assembly of FIG. 24;

FIG. 26 is a fragmentary, enlarged, horizontally cross-sectional viewfrom above an intermediate portion of the firing control assembly ofFIG. 24;

FIG. 27 is a fragmentary, enlarged, horizontally cross-sectional viewfrom above a distal portion of the firing control assembly of FIG. 24;

FIGS. 28 and 29 are shaded, fragmentary, enlarged, partially transparentperspective views of a staple cartridge removal assembly of the staplerof FIG. 1;

FIG. 30 is a bar graph illustrating a speed that a pinion moves a rackshown in FIG. 31 for various loads;

FIG. 31 is a fragmentary, perspective view of a simplified, exemplaryportion of a gear train according to the present invention between agear box and a rack;

FIG. 32 is a fragmentary, vertically longitudinal, cross-sectional viewof a distal end of an articulating portion of an exemplary embodiment ofan end effector with the inner tube, the pushrod-blade support, theanvil, the closure ring, and the near half of the staple sled removed;

FIG. 33 is a schematic circuit diagram of an exemplary switchingassembly for a power supply according to the invention;

FIG. 34 is a schematic circuit diagram of an exemplary switchingassembly for forward and reverse control of a motor according to theinvention; and

FIG. 35 is a schematic circuit diagram of another exemplary switchingassembly for the power supply and the forward and reverse control of themotor according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Aspects of the invention are disclosed in the following description andrelated drawings directed to specific embodiments of the invention.Alternate embodiments may be devised without departing from the spiritor the scope of the invention. Additionally, well-known elements ofexemplary embodiments of the invention will not be described in detailor will be omitted so as not to obscure the relevant details of theinvention.

Before the present invention is disclosed and described, it is to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only and is not intended to belimiting. It must be noted that, as used in the specification and theappended claims, the singular forms “a,” “an,” and “the” include pluralreferences unless the context clearly dictates otherwise.

While the specification concludes with claims defining the features ofthe invention that are regarded as novel, it is believed that theinvention will be better understood from a consideration of thefollowing description in conjunction with the drawing figures, in whichlike reference numerals are carried forward. The figures of the drawingsare not drawn to scale. Further, it is noted that the figures have beencreated using a computer-aided design computer program. This program attimes removes certain structural lines and/or surfaces when switchingfrom a shaded or colored view to a wireframe view. Accordingly, thedrawings should be treated as approximations and be used as illustrativeof the features of the present invention.

Referring now to the figures of the drawings in detail and first,particularly to FIGS. 1 to 2 thereof, there is shown an exemplaryembodiment of an electric surgical circular stapler 1. The presentapplication applies the electrically powered handle to a circularsurgical staple head for ease of understanding only. The invention isnot limited to circular staplers and can be applied to any surgicalstapling head, such as a linear stapling device, for example.

The powered stapler 1 has a handle body 10 containing three switches: ananvil open switch 20, an anvil close switch 21, and a staple firingswitch 22. Each of these switches is electrically connected to a circuitboard 500 (see FIG. 12) having circuitry programmed to carry out thestapling functions of the stapler 1. The circuit board 500 iselectrically connected to a power supply 600 contained within the handlebody 10. One exemplary embodiment utilizes 2 to 6 Lithium CR123 or CR2cells as the power supply 600. Other power supply embodiments arepossible, such as rechargeable batteries or a power converter that isconnected to an electric mains (in the latter embodiment, the staplerwould not be self-powered or self-contained). As used herein, the termsself-powered or self-contained when used with regard to the electricpower supply (600) are interchangeable and mean that the power supply isa complete and independent unit in and of itself and can operate underits own power without the use of external power sources. For example, apower supply having an electric cord that is plugged into an electricmains during use is not self-powered or self-contained.

Insulated conductive wires or conductor tracks on the circuit board 500connect all of the electronic parts of the stapler 1, such as an on/offswitch 12, a tissue compression indicator 14, the anvil and firingswitches 20, 21, 22, the circuit board 500, and the power supply 600,for example. But these wires and conductors are not shown in the figuresof the drawings for ease of understanding and clarity.

The distal end of the handle body 10 is connected to a proximal end of arigid anvil neck 30. Opposite this connection, at the distal end of theanvil neck 30, is a coupling device 40 for removably attaching a staplecartridge 50 and an anvil 60 thereto. Alternatively, the staplecartridge 50 can be non-removable in a single-use configuration of thestapler 1. These connections will be described in further detail below.

FIG. 2 shows the handle body 10 with the right half 13 of the handlebody 10 and the circuit board 500 removed. As will be discussed below, aproximal backbone plate 70 is also removed from the view of FIG. 2 toallow viewing of the internal components inside the handle body 10 fromthe right side thereof. What can be seen from the view of FIG. 2 is thatthere exist two internal component axes within the handle body 10. Afirst of these axes is the staple control axis 80, which is relativelyhorizontal in the view of FIG. 2. The staple control axis 80 is thecenterline on which lie the components for controlling staple actuation.The second of these axes is the anvil control axis 90 and is disposed atan angle to the staple control axis 80. The anvil control axis 90 is thecenterline on which lie the components for controlling anvil actuation.It is this separation of axes 80, 90 that allows the electric stapler 1to be powered using a handle body 10 that is small enough to fit in aphysician's hand and that does not take up so much space that thephysician becomes restricted from movement in all necessary directionsand orientations.

Shown inside the handle body 10 is the on/off switch 12 (e.g., a grenadepin) for controlling power (e.g., battery power) to all of theelectrical components and the tissue compression indicator 14. Thetissue compression indicator 14 indicates to the physician that thetissue being compressed between the anvil 60 and the staple cartridge 50has or has not been compressed with greater than a pre-set compressiveforce, which will be described in further detail below. This indicator14 is associated with a force switch 400 that has been described inco-pending U.S. Patent Provisional Application Ser. No. 60/801,989 filedMay 19, 2006, and titled “Force Switch” (the entirety of which isincorporated by reference herein).

The components along the anvil control axis 90 make up the anvil controlassembly 100. An anvil control frame 110 is aligned along the anvilcontrol axis 90 to house and/or fix various part of the anvil controlassembly 100 thereto. The anvil control frame 110 has a proximal mount112, an intermediate mount 114, and a distal mount 116. Each of thesemounts 112, 114, 116 can be attached to or integral with the controlframe 110. In the exemplary embodiment, for ease of manufacturing, theproximal mount 112 has two halves and is separate from the frame 110 andthe intermediate mount 114 is separate from the frame 110.

At the proximal end of the anvil control assembly 100 is an anvil motor120. The anvil motor 120 includes the drive motor and any gearbox thatwould be needed to convert the native motor revolution speed to adesired output axle revolution speed. In the present case, the drivemotor has a native speed of approximately 10,000 rpm and the gearboxconverts the speed down to between approximately 50 and 70 rpm at anaxle 122 extending out from a distal end of the anvil motor 120. Theanvil motor 120 is secured both longitudinally and rotationally insidethe proximal mount 112.

A motor-shaft coupler 130 is rotationally fixed to the axle 122 so thatrotation of the axle 122 translates into a corresponding rotation of themotor coupler 130.

Positioned distal of the coupler 130 is a rotating nut assembly 140. Thenut assembly 140 is, in this embodiment, a two part device having aproximal nut half 141 and a distal nut half 142 rotationally andlongitudinally fixed to the proximal nut half 141. It is noted thatthese nut halves 141, 142 can be integral if desired. Here, they areillustrated in two halves for ease of manufacturing. The proximal end ofthe nut assembly 140 is rotationally fixed to the distal end of thecoupler 130. Longitudinal and rotational support throughout the lengthof these two connected parts is assisted by the intermediate 114 anddistal 116 mounts.

A proximal nut bushing 150 (see FIG. 3) is interposed between theintermediate mount 114 and the proximal nut half 141 and a distal nutbushing 160 is interposed between the distal mount 116 and the distalnut half 142 to have these parts spin efficiently and substantiallywithout friction within the handle body 10 and the anvil control frame110. The bushings 150, 160 can be of any suitable bearing material, forexample, they can be of metal such as bronze or a polymer such as nylon.To further decrease the longitudinal friction between the rotating nutassembly 140 and the coupler 130, a thrust washer 170 is disposedbetween the proximal bushing 150 and the proximal nut half 141.

Rotation of the coupler 130 and nut assembly 140 is used to advance orretract a threaded rod 180, which is the mechanism through which theanvil 60 is extended or retracted. The threaded rod 180 is shown infurther detail in the exploded view of FIGS. 3 to 4 and is described infurther detail below. A rod support 190 is attached to a distal end ofthe anvil control frame 110 for extending the supporting surfaces insidethe nut assembly 140 that keep the rod 180 aligned along the anvilcontrol axis 90. The rod support 190 has a smooth interior shapecorresponding to an external shape of the portion of the rod 180 thatpasses therethrough. This mating of shapes allows the rod 180 to moveproximally and distally through the support 190 substantially withoutfriction. To improve frictionless movement of the rod 180 through thesupport 190, in the exemplary embodiment, a cylindrical rod bushing 192is disposed between the support 190 and the rod 180. The rod bushing 192is not visible in FIG. 2 because it rests inside the support 190.However, the rod bushing 192 is visible in the exploded view of FIGS. 3to 4. With the rod bushing 192 in place, the internal shape of thesupport 190 corresponds to the external shape of the rod bushing 192 andthe internal shape of the rod bushing 192 corresponds to the externalshape of the portion of the rod 180 that passes therethrough. The rodbushing 192 can be, for example, of metal such as bronze or a polymersuch as nylon.

The components along the staple control axis 80 form the staple controlassembly 200. The staple control assembly 200 is illustrated in FIG. 5viewed from a proximal upper and side perspective. The proximal end ofthe staple control assembly 200 includes a stapling motor 210. Thestapling motor 210 includes the drive motor and any gearbox that wouldbe needed to convert the native motor revolution speed to a desiredrevolution speed. In the present case, the drive motor has a nativespeed of approximately 20,000 rpm and the gearbox converts the speed toapproximately 200 rpm at an output axle 212 at the distal end of thegearbox. The axle 212 cannot be seen in the view of FIG. 5 but can beseen in the exploded view of FIGS. 6 to 7.

The stapling motor 210 is rotationally and longitudinally fixed to amotor mount 220. Distal of the motor mount 220 is an intermediatecoupling mount 230. This coupling mount 230 has a distal plate 232 thatis shown, for example in FIG. 6. The distal plate 232 is removable fromthe coupling mount 230 so that a rotating screw 250 can be heldtherebetween. It is this rotating screw 250 that acts as the drive forejecting the staples out of the staple cartridge 50. The efficiency intransferring the rotational movement of axle 212 to the rotating screw250 is a factor that can substantially decrease the ability of thestapler 1 to deliver the necessary staple ejection longitudinal force ofup to 250 pounds. Thus, an exemplary embodiment of the screw 250 has anacme profile thread.

There are two exemplary ways described herein for efficiently couplingthe rotation of the axle 212 to the screw 250. First, the stapling motor210 can be housed “loosely” within a chamber defined by the handle body10 so that it is rotationally stable but has play to move radially andso that it is longitudinally stable but has play to move. In such aconfiguration, the stapling motor 210 will “find its own center” toalign the axis of the axle 212 to the axis of the screw 250, which, inthe exemplary embodiment, is also the staple control axis 80.

A second exemplary embodiment for aligning the axle 212 and the screw250 is illustrated in FIGS. 1 to 5, for example. In this embodiment, aproximal end of a flexible coupling 240 is fixed (both rotationally andlongitudinally) to the axle 212. This connection is formed by fittingthe distal end of the axle 212 inside a proximal bore 241 of theflexible coupling 240. See FIG. 12. The axle 212 is, then, securedtherein with a proximal setscrew 213. The screw 250 has a proximalextension 251 that fits inside a distal bore 242 of the flexiblecoupling 240 and is secured therein by a distal setscrew 252. It isnoted that the figures of the drawings show the flexible coupling 240with ridges in the middle portion thereof. In an exemplary embodiment ofthe coupling 240, the part is of aluminum or molded plastic and has aspiral or helixed cut-out around the circumference of the center portionthereof. In such a configuration, one end of the coupling 240 can movein any radial direction (360 degrees) with respect to the other end (asin a gimbal), thus providing the desired flex to efficiently align thecentral axes of the axle 212 and the screw 250.

The proximal extension 251 of the screw 250 is substantially smaller indiameter than the diameter of the bore 231 that exists in and throughthe intermediate coupling mount 230. This bore 231 has two increasingsteps in diameter on the distal side thereof. The first increasing stepin diameter is sized to fit a proximal radius screw bushing 260, whichis formed of a material that is softer than the intermediate couplingmount 230. The proximal radius screw bushing 260 only keeps the screw250 axially aligned and does not absorb or transmit any of thelongitudinal thrust. The second increasing step in diameter is sized tofit a proximal thrust bearing 270 for the screw 250. In an exemplaryembodiment of the thrust bearing 270, proximal and distal platessandwich a bearing ball retainer plate and bearing balls therebetween.This thrust bearing 270 absorbs all of the longitudinal thrust that isimparted towards the axle 212 while the up to 250 pounds of longitudinalforce is being applied to eject the staples in the staple cartridge 50.The proximal extension 251 of the screw 250 has different sizeddiameters for each of the interiors of the screw bushing 260 and thethrust bearing 270. The motor mount 220 and the coupling mount 230,therefore, form the two devices that hold the flexible coupling 240therebetween.

The rotating screw 250 is held inside the distal plate 232 with a distalradius screw bushing 280 similar to the proximal radius screw bushing260. Thus, the screw 250 rotates freely within the distal plate 232. Totranslate the rotation of the screw 250 into a linear distal movement,the screw 250 is threaded within a moving nut 290. Movement of the nut290 is limited to the amount of movement that is needed for completeactuation of the staples; in other words, the nut 290 only needs to movethrough a distance sufficient to form closed staples between the staplecartridge 50 and the anvil 60 and to extend the cutting blade, if any,within the staple cartridge 50, and then retract the same. When the nut290 is in the proximal-most position (see, e.g., FIG. 12), the staplesare at rest and ready to be fired. When the nut 290 is in thedistal-most position, the staples are stapled through and around thetissue interposed between the staple cartridge 50 and the anvil, and theknife, if any, is passed entirely through the tissue to be cut. Thedistal-most position of the nut 290 is limited by the location of thedistal plate 232. Thus, the longitudinal length of the threads of thescrew 250 and the location of the distal plate 232 limit the distalmovement of the nut 290.

Frictional losses between the screw 250 and the nut 290 contribute to asignificant reduction in the total pounds of force that can betransmitted to the staple cartridge 50 through the cartridge plunger320. Therefore, it is desirable to select the materials of the screw 250and the nut 290 and the pitch of the threads of the screw 250 in anoptimized way. It has been found that use of a low-friction polymer formanufacturing the nut 290 will decrease the friction enough to transmitthe approximately 250 pounds of longitudinal force to the distal end ofthe cartridge plunger 320—the amount of force that is needed toeffectively deploy the staples. Two particular exemplary materialsprovide the desired characteristics and are referred to in the art asDELRIN® AF Blend Acetal (a thermoplastic material combining TEFLON®fibers uniformly dispersed in DELRIN® acetal resin) and RULON® (acompounded form of TFE fluorocarbon) or other similar low-frictionpolymers.

A nut-coupling bracket 300 is longitudinally fixed to the nut 290 sothat it moves along with the nut 290. The nut-coupling bracket 300provides support for the relatively soft, lubricious nut material. Inthe exemplary embodiment shown, the bracket 300 has an interior cavityhaving a shape corresponding to the exterior shape of the nut 290. Thus,the nut 290 fits snugly into the coupling bracket 300 and movement ofthe nut 290 translates into a corresponding movement of the nut-couplingbracket 300. The shape of the nut-coupling bracket 300 is, in theexemplary embodiment, dictated by the components surrounding it and bythe longitudinal forces that it has to bear. For example, there is aninterior cavity 302 distal of the nut 290 that is shaped to receive thedistal plate 232 therein. The nut-coupling bracket 300 also has a distalhousing 304 for receiving therein a stiffening rod 310. The stiffeningrod 310 increases the longitudinal support and forms a portion of theconnection between the nut 290 and a cartridge plunger 320 (see, i.e.,FIG. 5), which is the last moving link between elements in the handlebody 10 and the staple cartridge 50. A firing bracket 330, disposedbetween the distal end of the nut-coupling bracket 300 and thestiffening rod 310, strengthens the connection between the nut-couplingbracket 300 and the rod 310.

Various components of the stapler 1 are connected to one another to forma backbone or spine. This backbone is a frame providingmulti-directional stability and is made up of four primary parts (inorder from proximal to distal): the anvil control frame 110, theproximal backbone plate 70 (shown in FIGS. 3 to 4 and 6 to 7), a distalbackbone plate 340, and the anvil neck 30. Each of these four parts islongitudinally and rotationally fixed to one another in this order andforms the skeleton on which the remainder of the handle components isattached in some way. Lateral support to the components is provided bycontours on the inside surfaces of the handle body 10, which in anexemplary embodiment is formed of two halves, a left half 11 and a righthalf 13. Alternatively, support could be single frame, stamped, orincorporated into the handle halves 11, 13.

Functionality of the anvil control assembly 100 is described with regardto FIGS. 17 to 27. To carry out a stapling procedure with the stapler 1,the anvil 60 is removed entirely from the stapler 1 as shown in FIG. 17.The anvil open switch 20 is depressed to extend the distal end of thetrocar tip 410 housed within the staple cartridge and which islongitudinally fixedly connected to the screw 250. The point of thetrocar tip 410 can, now, be passed through or punctured through tissuethat is to be stapled. The user can, at this point, replace the anvil 60onto the trocar tip 410 from the opposite side of the tissue (see FIG.18) and, thereby, lock the anvil 60 thereon. The anvil closed switch 22can be actuated to begin closing the anvil 60 against the staplecartridge 50 and pinch the tissue therebetween within an anvil-cartridgegap 62.

To describe how the trocar tip controlling movement of the anvil 60occurs, reference is made to FIGS. 8 to 10, 14 to 15, and 18. As shownin dashed lines in FIG. 15, a rod-guiding pin 143 is positioned withinthe central bore 144 of the distal nut half 142. As the threaded rod 180is screwed into the rotating nut 140, 141, 142, the pin 143 catches theproximal end of the thread 182 to surround the pin 143 therein. Thus,rotation of the nut 140 with the pin 143 inside the thread 182 willcause proximal or distal movement of the rod 180, depending on thedirection of nut rotation. The thread 182 has a variable pitch, as shownin FIGS. 14 to 15, to move the anvil 60 at different longitudinalspeeds. When the pin 143 is inside the longer (lower) pitched threadportion 183, the anvil 60 moves longitudinally faster. In comparison,when the pin 143 is inside the shorter (higher) pitched thread portion184, the anvil 60 moves longitudinally slower. It is noted that the pin143 is the only portion contacting the thread 182 when in the longerpitched thread portion 183. Thus, the pin 143 is exposed to the entirelongitudinal force that is acting on the rod 180 at this point in time.The pin 143 is strong enough to bear such forces but may not besufficient to withstand all longitudinal force that could occur withanvil 60 closure about interposed tissue.

As shown in FIG. 14, the rod 180 is provided with a shorter pitchedthread portion 184 to engage in a corresponding internal thread 145 atthe proximal end of the central bore 144 of the proximal nut half 141.When the shorter pitched thread portion 184 engages the internal thread145, the entire transverse surface of the thread portion 184 contactsthe internal thread 145. This surface contact is much larger than thecontact between the pin 143 and any portion of the thread 182 and,therefore, can withstand all the longitudinal force that occurs withrespect to anvil 60 closure, especially when the anvil 60 is closingabout tissue during the staple firing state. For example, in theexemplary embodiment, the pin 143 bears up to approximately 30 to 50pounds of longitudinal force. This is compared to the threads, which canhold up to 400 pounds of longitudinal force—an almost 10-to-1difference.

An alternative exemplary embodiment of anvil control assembly 100 canentirely remove the complex threading of the rod 180. In such a case,the rod 180 has a single thread pitch and the anvil motor 120 is driven(through corresponding programming in the circuit board 500) atdifferent speeds dependent upon the longitudinal position of thesingle-thread rod 180.

In any embodiment for driving the motors 120, 210, the controlprogramming can take many forms. In one exemplary embodiment, themicrocontroller on the battery powered circuit board 500 can apply pulsemodulation (e.g., pulse-width, pulse-frequency) to drive either or bothof the motors. Further, because the stapler 1 is a device that has a lowduty cycle, or is a one-use device, components can be driven to exceedacceptable manufacturers' specifications. For example, a gear box can betorqued beyond its specified rating. Also, a drive motor, for example, a6 volt motor, can be overpowered, for example, with 12 volts.

Closure of the anvil 60 from an extended position to a position in whichthe tissue is not compressed or is just slightly compressed can occurrapidly without causing damage to the interposed tissue. Thus, thelonger-pitched thread portion 183 allows the user to quickly close theanvil 60 to the tissue in a tissue pre-compressing state. Thereafter, itis desirable to compress the tissue slowly so that the user has controlto avoid over-compression of the tissue. As such, the shorter pitchedthread portion 184 is used over this latter range of movement andprovides the user with a greater degree of control. During suchcompression, the force switch 400 seen in FIG. 18 and described inco-pending U.S. Patent Provisional Application Ser. No. 60/801,989 canbe used to indicate to the user through the tissue compression indicator14 (and/or to the control circuitry of the circuit board 500) that thetissue is being compressed with a force that is greater than thepre-load of the spring 420 inside the force switch 400. Depending on theconfiguration of the force switch 400, the force on the switch can beproportional or can be equal. It is noted that FIG. 18 illustrates theforce switch 400 embodiment in the normally-open configuration describedas the first exemplary embodiment of U.S. Patent Provisional ApplicationSer. No. 60/801,989. A strain gauge can also be used for measuringtissue compression.

FIGS. 19 to 23 illustrate movement of the rod 180 from an anvil-extendedposition (see FIGS. 19 to 20), to a 1-cm-closure-distance position (seeFIG. 21), to a staple-fire-ready position (see FIG. 22), and, finally,to an anvil fully closed position (see FIG. 23). Movement of the rod 180is controlled electrically (via the circuit board 500) by contactbetween a portion of a cam surface actuator 185 on the rod 180 andactuating levers or buttons of a series of micro-switches positioned inthe handle body 10.

A rod-fully-extended switch 610 (see FIG. 19) is positioned distal inthe handle body 10 to have the actuator 185 compress the activationlever of the rod-fully-extended switch 610 when the rod 180 (and,thereby, the anvil 60) is in the fully extended position. A 1-cm switch612 is positioned in an intermediate position within the handle body 10(see FIGS. 20 to 21) to prevent a 1-cm cam surface portion 186 of therod 180 from pressing the activation button of the 1-cm switch 612 whenthe rod 180 (and, thereby, the anvil 60) is within 1 cm of the fullyclosed position. After passing the 1-cm closure distance, as shown inFIG. 22, the cam surface actuator 185 engages a staple-fire-ready switch614. The lower end of the actuator 185 as viewed in FIGS. 22 to 23 has abevel on both the forward and rear sides with respect to the button ofthe staple-fire-ready switch 614 and the distance between the portion onthe two bevels that actuates the button (or, only the flat portionthereof) corresponds to the acceptable staple forming range (i.e., safefiring length) of the staples in the staple cartridge 50. Thus, when thebutton of the staple-fire-ready switch 614 is depressed for the firsttime, the distance between the anvil 60 and the staple cartridge 50 isat the longest range for successfully firing and closing the staples.While the button is depressed, the separation distance 62 of the anvil60 (see FIG. 18) remains within a safe staple-firing range. However,when the button of the staple-fire-ready switch 614 is no longerdepressed—because the actuator 185 is positioned proximally of thebutton, then staples will not fire because the distance is too short fortherapeutic stapling. FIG. 23 show the rod 180 in the proximal-mostposition, which is indicated by the top end of the actuator 185 closingthe lever of a rod fully-retracted switch 616. When this switch 616 isactuated, the programming in the circuit board 500 prevents the motor120 from turning in a rod-retraction direction; in other words, it is astop switch for retracting the rod 180 in the proximal direction.

It is noted that FIGS. 2 to 3, 11 to 12, and 16 illustrate the distalend of the rod 180 not being connected to another device at its distalend (which would then contact the proximal end of the force switch 400).The connection band or bands between the distal end of the rod 180 andthe proximal end of the force switch 400 are not shown in the drawingsonly for clarity purposes. In an exemplary embodiment, the pull-bandsare flat and flexible to traverse the curved underside of the cartridgeplunger 320 through the anvil neck 30 and up to the proximal end of theforce switch 400. Of course, if the force switch 400 is not present, thebands would be connected to the proximal end of the trocar tip 410 thatreleasably connects to the proximal end of the anvil 60.

Functionality of the staple control assembly 200 is described withregard to FIGS. 12 to 16 and 24 to 27, in particular, to FIG. 24. Thestapling motor 210 is held between a motor bearing 222 and a motor shaftcover 224. The axle 212 of the stapling motor 210 is rotationallyconnected to the proximal end of the flexible coupling 240 and thedistal end of the flexible coupling 240 is rotationally connected to theproximal end of the screw 250, which rotates on bearings 260, 270, 280that are disposed within the intermediate coupling mount 230 and thedistal plate 232. The longitudinally translating nut 290 is threadedonto the screw 250 between the coupling mount 230 and the distal plate232. Therefore, rotation of the axle 212 translates into a correspondingrotation of the screw 250.

The nut-coupling bracket 300 is longitudinally fixed to the nut 290 andto the stiffening rod 310 and the firing bracket 330. The firing bracket330 is longitudinally fixed to the cartridge plunger 320, which extends(through a non-illustrated staple driver) up to the staple cartridge 50(or to the staples). With such a connection, longitudinal movement ofthe nut 290 translates into a corresponding longitudinal movement of thecartridge plunger 320. Accordingly, when the staple firing switch 22 isactivated, the stapling motor 210 is caused to rotate a sufficientnumber of times so that the staples are completely fired from the staplecartridge 50 (and the cutting blade, if present, is extended tocompletely cut the tissue between the anvil 60 and the staple cartridge50). Programming in the circuitry, as described below, then causes thecartridge plunger 320 to retract after firing and remove any portion ofthe staple firing parts and/or the blade within the staple cartridge 50from the anvil-cartridge gap 62.

Control of this stapling movement, again, occurs through micro-switchesconnected to the circuit board 500 through electrical connections, suchas wires. A first of these control switches, the proximal staple switch618, controls retraction of the staple control assembly 200 and definesthe proximal-most position of this assembly 200. To actuate this switch,an actuation plate 306 is attached, in an adjustable manner, to a sideof the nut-coupling bracket 300. See, e.g., FIGS. 6 and 24. As such,when the nut 290 moves proximally to cause the plate 306 on the nutcoupling bracket 300 to activate the proximal staple switch 618, powerto the stapling motor 210 is removed to stop further proximally directedmovement of the staple control assembly 200.

A second of the switches for controlling movement of the staple controlassembly 200 is located opposite a distal transverse surface of thestiffening rod 310. See, e.g. FIG. 27. At this surface is disposed alongitudinally adjustable cam member 312 that contacts a distal stapleswitch 620. In an exemplary embodiment, the cam member 312 is a screwthat is threaded into a distal bore of the stiffening rod 310.Accordingly, when the nut 290 moves distally to cause the cam member 312of the stiffening rod 310 to activate the distal staple switch 620,power to the stapling motor 210 is removed to stop further distallydirected movement of the staple control assembly 200.

FIGS. 28 and 29 illustrate a removable connection assembly to permitreplacement of a different staple cartridge 50 on the distal end of theanvil 30.

The proximal-most chamber of the handle body 10 defines a cavity forholding therein a power supply 600. This power supply 600 is connectedthrough the circuit board 500 to the motors 120, 210 and to the otherelectrical components of the stapler 1.

The electronic components of the stapler 1 have been described ingeneral with respect to control through the circuit board 500. Theelectric stapler 1 includes, as set forth above in an exemplaryembodiment, two drive motors 120, 210 powered by batteries andcontrolled through pushbuttons 20, 21, 22. The ranges of travel of eachmotor 120, 210 are controlled by limit switches 610, 616, 618, 620 atthe ends of travel and at intermediary locations 612, 614 along thetravel. The logic by which the motors 120, 210 are controlled can beaccomplished in several ways. For example, relay, or ladder logic, canbe used to define the control algorithm for the motors 120, 210 andswitches 610, 612, 614, 616, 618, 620. Such a configuration is a simplebut limited control method. A more flexible method employs amicroprocessor-based control system that senses switch inputs, locksswitches out, activates indicator lights, records data, provides audiblefeedback, drives a visual display, queries radio frequencyidentification devices (RFIDs), senses forces, communicates withexternal devices, monitors battery life, etc. The microprocessor can bepart of an integrated circuit constructed specifically for the purposeof interfacing with and controlling complex electro-mechanical systems.Examples of such chips include those offered by Atmel, such as the Mega128, and by PIC, such as the PIC 16F684.

A software program is required to provide control instructions to such aprocessor. Once fully developed, the program can be written to theprocessor and stored indefinitely. Such a system makes changes to thecontrol algorithm relatively simple; changes to the software that areuploaded to the processor adjust the control and user interface withoutchanging the wiring or mechanical layout of the device.

For a disposable device, a power-on event is a one time occurrence. Inthis case, the power-on can be accomplished by pulling a tab or arelease that is permanently removed from the device. The removal enablesbattery contact, thus powering on the device.

In any embodiment of the device, when the device is powered on, thecontrol program begins to execute and, prior to enabling the device foruse, goes through a routine that ensures awareness of actual positionsof the extend/retract and firing sub-assemblies, referred to as a homingroutine. The homing routine may be executed at the manufacturer prior toshipping to the user. In such a case, the homing routine is performed,the positions of the assemblies are set, and the device is shipped tothe user in a ready-to-use condition. Upon power-up, the device verifiesits positions and is ready to use.

Visual indicators (e.g., LEDs) are used to provide feedback to the user.In the case of the pushbutton switches 20, 21, 22, they can be lit (orbacklit) when active and unlit when not active. The indicators can blinkto convey additional information to the user. In the case of a delayedresponse after a button press, a given light can blink at anever-increasing rate as the response becomes imminent, for example. Theindicators can also light with different colors to indicate variousstates.

Cams are used in various locations at the stapler 1 to activate limitswitches that provide position information to the processor. By usinglinear cams of various lengths, position ranges can be set.Alternatively, encoders can be used instead of limit switches (absoluteand incremental positioning). Limit switches are binary: off or on.Instead of binary input for position information, encoders (such asoptical encoders) can be used to provide position information. Anotherway to provide position feedback includes mounting pulse generators onthe end of the motors that drive the sub-assemblies. By counting pulses,and by knowing the ratio of motor turns to linear travel, absoluteposition can be derived.

Use of a processor creates the ability to store data. For example,vital, pre-loaded information, such as the device serial number andsoftware revision can be stored. Memory can also be used to record datawhile the stapler 1 is in use. Every button press, every limit switchtransition, every aborted fire, every completed fire, etc., can bestored for later retrieval and diagnosis. Data can be retrieved througha programming port or wirelessly. In an exemplary embodiment, the devicecan be put into diagnostic mode through a series of button presses. Inthis diagnostic mode, a technician can query the stapler 1 for certaindata or to transmit/output certain data. Response from the stapler 1 tosuch a query can be in the form of blinking LEDs, or, in the case of adevice with a display, visual character data, or can be electronic data.As set forth above, a strain gauge can be used for analog output and toprovide an acceptable strain band. Alternatively, addition of a secondspring and support components can set this band mechanically.

An exemplary control algorithm for a single fire stapler 1 can includethe following steps:

-   -   Power on.    -   Verify home position and go to home position, if        necessary/desired.    -   Enable extend/retract buttons (lit) and disable (unlit) staple        fire button.    -   Enable staple fire button only after full extension (anvil        removal) and subsequent retraction with extend/retract buttons        remaining enabled.    -   Upon actuation of staple fire button, retract anvil until force        switch is activated.    -   Begin countdown by blinking fire button LED and increase blink        rate as firing cycle becomes imminent. Continue monitoring of        force switch and retract anvil so that force switch remains        activated.    -   During staple fire cycle, any button press aborts staple fire        routine.    -   If abort occurs before staple firing motor is activated, firing        cycle stops, anvil is extended to home position, and staple fire        button remains active and ready for a re-fire.    -   Alternatively, if the abort occurs during movement of firing        motor, firing cycle stops, firing motor is retracted, anvil is        returned to home position, and firing button is rendered        inactive. Accordingly, stapler (or that staple cartridge) cannot        be used.    -   After countdown to fire is complete, staple range limit switch        is queried for position. If staple range limit switch is        activated—meaning that anvil is within an acceptable staple        firing range—then staple firing motor is activated and firing        cycle proceeds. If staple range limit switch is not activated,        then firing cycle is aborted, anvil is returned to home        position, and staple firing button remains active ready for a        re-fire attempt.    -   After a completed staple firing, anvil remains in closed        position and only the extend button remains active. Once anvil        is extended to at least the home position, both extend and        retract buttons are made active. Staple fire button remains        inactive after a completed staple firing.        Throughout the above exemplary cycle, button presses, switch        positions, aborts, and/or fires can be recorded.

In a surgical procedure, the stapler is a one-way device. In the testmode, however, the test user needs to have the ability to move thetrocar 410 and anvil 60 back and forth as desired. The power-on featurepermits entry by the user into a manual mode for testing purposes. Thistest mode can be disengaged and the stapler reset to the use mode forpackaging and shipment.

For packaging, it is desirable (but not necessary) to have the anvil 60be disposed at a distance from the staple cartridge 50. Therefore, ahoming sequence can be programmed to place the anvil 60 one centimeter(for example) away from the staple cartridge 50 before powering down forpackaging and shipment.

When the electric stapler is unpackaged and ready to be used forsurgery, the user turns the stapler on (switch 12). Staples should notbe allowed to fire at any time prior to being in a proper staple-firingposition and a desired tissue compression state. Thus, the anvil/trocarextend/retract function is the only function that is enabled. In thisstate, the extend and retract buttons 20, 21 are lit and the staplefiring switch 22 is not lit (i.e., disabled).

Before use inside the patient, the trocar 410 is extended and the anvil60 is removed. If the stapler is being used to anastomose a colon, forexample, the trocar 410 is retracted back into the anvil neck 30 and thestaple cartridge 50 and anvil neck 30 are inserted trans-anally into thecolon to a downstream side of the dissection. The anvil 60, in contrast,is inserted through an upstream laparoscopic incision and placed at theupstream side of the dissection. The anvil 60 is attached to the trocar410 and the two parts are retracted towards the staple cartridge 50until a staple ready condition occurs. As set forth above, the anvil ismoved to a distance that does not substantially compress and,specifically, does not desiccate, the tissue therebetween. At thispoint, staple firing can occur when desired.

The staple firing sequence is started by activating the staple fireswitch 22. Staple firing can be aborted anytime during the firingsequence, whether prior to movement (during the blanching cycle) orduring movement (whether the staples have started to form or not). Thesoftware is programmed to begin a staple firing countdown sequencebecause it is understood that the tissue needs to be compressed andallowed to desiccate before staple firing should occur. Thus, after thestaple firing switch 22 is activated, the anvil 60 closes upon theinterposed tissue and begins to compress the tissue. The staple firingsequence includes an optimal tissue compression (OTC) measurement and afeedback control mechanism that causes staples to be fired only when thecompression is in a desired pressure range, referred to as the OTCrange, and a sufficient time period has elapsed to allow fluid removalfrom the compressed tissue. The OTC range is known beforehand based uponknown characteristics of the tissue that is to be compressed between theanvil 60 and the staple cartridge 50 (the force switch can be tuned fordifferent tissue OTC ranges). It is the force switch 400 that providesthe OTC measurement and supplies the microprocessor with informationindicating that the OTC for that particular tissue has been reached. TheOTC state can be indicated to the user with an LED, for example.

When the firing sequence begins, the staple fire switch 22 can be madeto blink at a given rate and then proceed to blink faster and faster,for example, until firing occurs. If no abort is triggered during thiswait time, the OTC state will remain for the preprogrammed desiccationduration and staple filing will occur after the countdown concludes. Inthe example of colon anastomosis with a circular stapler, stapling ofthe dissection occurs simultaneously with a cutting of tissue at thecenter of the dissection. This cutting guarantees a clear opening in themiddle of the circular ring of staples sufficient to create an openingfor normal colon behavior after the surgery is concluded.

As the liquid from the interposed compressed tissue is removed, thecompressive force on the tissue naturally reduces. In some instances,this reduction can be outside the OTC range. Therefore, the programincludes closed-loop anvil-compression control that is dependent uponcontinuous measurements provided by the force switch 400. With thisfeedback, the compressed tissue is kept within the OTC range throughoutthe procedure and even after being desiccated.

During the staple firing cycle, any actuation of a control switch by theuser can be programmed to abort the staple fire routine. If an abortoccurs before the staple firing motor 210 is activated, the firing cyclestops, the anvil 60 is extended to a home position, and the staple fireswitch 22 remains active and ready for a re-fire attempt, if desired.Alternatively, if the abort occurs during movement of the staple firingmotor 210, the firing cycle stops and the staple firing motor 210 iscaused to extend the anvil 60 to its home position. At this point, thestaple firing switch 22 is rendered inactive. Accordingly, the stapler(or that particular staple cartridge) can no longer be used (unless thestaple cartridge is replaced).

It is noted that before a staple firing can occur, a staple range limitswitch is queried for relative position of the staple cartridge 50 andanvil 60. If the staple range limit switch is activated—meaning thatanvil 60 is within an acceptable staple firing range—then the staplefiring motor 210 can be made active and the firing cycle can be allowedto proceed. If the staple range limit switch is not activated, then thefiring cycle is aborted, the anvil 60 is returned to the home position,and the staple firing switch 22 remains active and ready for a re-fireattempt.

Powering (also referred to as actuating, powering, controlling, oractivating) of the motor and/or the drive train of any portion of theend effector (e.g., anvil or stapler/cutter) is described herein. It isto be understood that such powering need not be limited to a singlepress of an actuation button by the user nor is the powering of a motorlimited to a single energizing of the motor by the power supply. Controlof any motor in the device can require the user to press an actuationbutton a number of times, for example, a first time to actuate a portionof the end effector for a first third of movement, a second time for asecond third of movement, and a third time for a last third of movement.More specifically for a surgical stapler, a first exemplary actuationcan move the staple sled or blade past the lock-out, a second exemplaryactuation can move the part up to the tissue, and a third exemplaryactuation can move the sled past all staples to the end of the staplecartridge. Similarly, powering of a motor need not be constant, forexample, where the motor is energized constantly from the time that theblade begins movement until it reaches the end point of its movement.Instead, the motor can be operated in a pulsed mode, a first example ofwhich includes periodically switching on and off the power supplied bythe power supply to the motor during actuation of an end effectorfunction. More specifically for a stapler, the motor can be pulsed tentimes/second as the staple/cutter moves from its proximal/start positionto its distal-most position. This pulsing can be directly controlled orcontrolled by microprocessor, either of which can have an adjustablepulse rate. Alternatively, or additionally, the motor can be operatedwith a pulse modulation (pulse-width or pulse-frequency), with pulsesoccurring at very short time periods (e.g., tenths, hundredths,thousandths, or millionths of a second). Accordingly, when the powersupply, the motor, and/or the drive train are described herein as beingpowered, any of these and other possible modes of operation areenvisioned and included.

After a completed staple firing, the anvil 60 remains in the closedposition and only the extend switch 20 remains active (all otherswitches are deactivated). Once the anvil 60 is extended to at least thehome position, both the extend and retract switches 20, 21 are madeactive but the retraction switch 21 does not permit closure of the anvil60 past the home position. The staple fire switch 22 remains inactiveafter a completed staple firing.

As set forth above, the anvil neck 30 houses a linear force switch 400connected to the trocar 410. This switch 400 is calibrated to activatewhen a given tensile load is applied. The given load is set tocorrespond to a desired pressure that is to be applied to the particulartissue before stapling can occur. Interfacing this switch 400 with theprocessor can ensure that the firing of staples only occurs within theOTC range.

The following text is an exemplary embodiment of a program listing forcarrying out the methods according to the invention as described herein.The text that follows is only submitted as exemplary and those of skillin the art can appreciate that programming the methods according to theinvention can take many different forms to achieve the samefunctionality.

Also mentioned above is the possibility of using RFIDs with a staplecartridge and an RFID interface for sensing compatible staplecartridges. In the case of a stapler that uses re-loadable staplecartridges, such as the stapler 1 described herein, an RFID can beplaced in the staple cartridge to ensure compatibility with theparticular stapler and, also, to track usage and inventory. In such aconfiguration, the stapler includes an RFID reader that interrogates theRFID mounted in the cartridge. The RFID responds with a unique code thatthe stapler verifies. If the stapler cartridge is verified, the staplerbecomes active and ready for use. If the cartridge is rejected, however,the stapler gives a rejected indication (e.g., a blinking LED, anaudible cue, a visual indicator). To avoid accidental or improperreading of a nearby staple cartridge, the antenna of the RFID reader canbe constructed to only read the RFID when the staple cartridge isinstalled in the stapler or is very nearby (optimally, at the distal endof the device). Use of the RFID can be combined with a mechanicallockout to ensure that only one fire cycle is allowed per staplecartridge.

In the unlikely event that the stapler becomes inoperable during use, amechanical override or bail-out is provided to allow manual removal ofthe device from the patient.

As described above, the present invention is not limited to a circularstapler, which has been used as an exemplary embodiment above, and canbe applied to any surgical stapling head, such as a linear staplingdevice, for example. Accordingly, a linear stapler is being used in thetext that follows for various exemplary embodiments. However, use of alinear stapler in this context should not be considered as limited onlythereto.

Described above are components that exist along the staple control axis80 and that form the staple control assembly 200. As set forth therein,the required force for proper staple ejection and tissue cutting can beover 200 pounds and, possibly, up to 250 pounds. It has been determinedthat minimum requirements for carrying out the desired stapling andcutting functions with the electric surgical stapler for human tissue(such as colon tissue, for example) are:

-   -   1) delivering approximately 54.5 kg (120 pounds) of force over a        stroke of about 60 mm (−2.4″) in approximately 3 seconds; or    -   2) delivering approximately 82 kg (180 pounds) of force over a        stroke of about 60 mm (−2.4″) in approximately 8 seconds.        The electric-powered, hand-held surgical stapling device of the        present invention can meet these requirements because it is        optimized in a novel way as set forth below.

To generate the force necessary to meet the above-mentionedrequirements, the maximum power (in watts) of the mechanical assemblyneeds to be calculated based upon the maximum limits of theserequirements: 82 kg over 60 mm in 3 seconds. Mathematical conversion ofthese figures generates an approximate maximum of 16 Watts of mechanicalpower needed at the output of the drive train. Conversion of theelectrical power into mechanical power is not 1:1 because the motor hasless than 100% efficiency and because the drive train also has less than100% efficiency. The product of these two efficiency ratings forms theoverall efficiency. The electrical power required to produce the 16Watts of mechanical power is greater than the 16 Watts by an inverseproduct of the overall efficiency. Once the required electrical powercan be determined, an examination of available power supplies can bemade to meet the minimum power requirements. Thereafter, an examinationand optimization of the different power supplies can be made. Thisanalysis is described in detail in the following text.

Matching or optimizing the power source and the motor involves lookinginto the individual characteristics of both. When examining thecharacteristics of an electric motor, larger motors can perform a givenamount of work with greater efficiency than smaller motors. In addition,motors with rare-earth magnets or with coreless construction can deliverthe same power in a smaller size, but at higher cost. Further, ingeneral, larger motors cost less than smaller motors if both aredesigned to deliver the same power over a given period of time. Largermotors, however, have an undesirable characteristic when used insurgical stapling devices because the handle in which they are to beplaced is limited by the size of an operator's hand. Physicians desireto use devices that are smaller and lighter, not larger and heavier.Based upon these considerations, cost, size, and weight are factors thatcan be optimized for use in the surgical stapler handle of the presentinvention.

Available motors for use within a physician's hand include motors withrelatively inexpensive ceramic magnets and motors with relativelyexpensive rare earth (i.e., neodymium) magnets. However, the powerincrease of the latter as compared to the former is not sufficientlylarge to warrant the substantial increase in cost of the latter. Thus,ceramic magnet motors can be selected for use in the handle. Exemplarymotors come in standard sizes (diameter) of 27.5 mm or 24 mm, forexample. These motors have a rated efficiency of approximately 60%(which decreases to 30% or below depending upon the size of the load).Such motors operate at speeds of approximately 30,000 rpm (between20,000 and 40,000 rpm) when unloaded.

Even though such conventional motors could be used, it would bedesirable to reduce the size even further. To that effect, the inventorshave discovered that coreless, brush-type, DC motors produce similarpower output but with a significant reduction in size. For example, a 17mm diameter coreless motor can output approximately the same power as astandard 24 mm diameter motor. Unlike a standard motor, the corelessmotor can have an efficiency of up to 80%. Coreless motors almost alluse rare earth magnets.

With such a limited volume and mechanical power available, it isdesirable to select a mechanical gear train having the greatestefficiency. Placing a rack and pinion assembly as the final drive traincontrol stage places a high-efficiency end stage in the drive train ascompared to a screw drive because, in general, the rack and pinion hasan approximate 95% efficiency, and the screw drive has a maximum ofabout 80% efficiency. For the linear electric stapler, there is a 60 mmtravel range for the stapling/cutting mechanism when the stapler has a60 mm cartridge (cartridges ranging from 30 mm to 100 mm can be used but60 mm is used in this example for illustrative purposes). With thistravel range, a 3-second, full travel duration places the rack andpinion extension rate at 0.8 inches per second. To accomplish this witha reasonably sized rack and pinion assembly, a gear train should reducethe motor output to approximately 60 rpm. With a motor output speed ofapproximately 30,000 rpm, the reduction in speed for the drive trainbecomes approximately 500:1. To achieve this reduction with the motor, a5-stage drive train is selected. It is known that such drive trains havean approximate 97% efficiency for each stage. Thus, combined with anapproximate 95% efficiency of the rack and pinion, the overallefficiency of the drive train is (0.95)(0.97)⁵ or 82%. Combining the 60%motor efficiency with the 82% drive train efficiency yields an overallelectrical to final mechanical efficiency of approximately 49.2%.Knowing this overall efficiency rating, when determining the amount ofelectrical power required for operating the stapler within the desiredrequirements, the actual electrical power needed is almost twice thevalue that is calculated for producing the stapling/cutting force.

To generate the force necessary to meet the above-mentionedrequirements, the power (in watts) of the mechanical assembly can becalculated based upon the 82 kg over 60 mm in 3 seconds to beapproximately 16 Watts. It is known that the overall mechanicalefficiency is 49.2%, so 32.5 Watts is needed from the power supply (16mech. watts≈32.5 elec. Watts×0.492 overall efficiency.). With thisminimum requirement for electrical power, the kind of cells available topower the stapler can be identified, which, in this case, includehigh-power Lithium Primary cells. A known characteristic of high-powerLithium cells (e.g., CR123 or CR2 cells) is that they produce about 5peak watts of power per cell. Thus, at least six cells in series willgenerate the required approximate amount of 32.5 watts of electricalpower, which translates into 16 watts of mechanical power. This does notend the optimization process because each type of high-power Lithiumcell manufactured has different characteristics for delivering peakpower and these characteristics differ for the load that is to beapplied.

Various battery characteristics exist that differentiate one battery ofa first manufacturer from another battery of a second manufacturer.Significant battery characteristics to compare are those that limit thepower that can be obtained from a battery, a few of which include:

-   -   type of electrolyte in the cell;    -   electrolyte concentration and chemistry;    -   how the anode and cathode are manufactured (both in chemistry        and in mechanical construction); and    -   type and construction of the PTC (positive temperature        coefficient of resistance) device.        Testing of one or more of these characteristics gives valuable        information in the selection of the most desirable battery for        use in the stapling device. It has been found that an        examination of the last characteristic—PTC device        behavior—allows an optimization of the type of battery to        perform the desired work.

Most power sources are required to perform, with relative certainty andefficiency, many times throughout a long period of time. When designingand constructing a power source, it is not typical to select the powersource for short-duration use combined with a low number of uses.However, the power source of an electric stapling device is only usedfor a short duration and for a small number of times. In each use, themotor needs to be ready for a peak load and needs to perform withouterror. This means that, for surgical staplers, the stapling/cuttingfeature will be carried out during only one medical procedure, which hascycle counts of between 10 and 20 uses at most, with each use needing toaddress a possible peak load of the device. After the one procedure, thedevice is taken out of commission and discarded. Therefore, the powersource for the present invention needs to be constructed unlike anyother traditional power supply.

The device according to the present invention is constructed to have alimited useful life of a power cell as compared to an expected usefullife of the power cell when not used in the device. When so configured,the device is intended to work few times after this defined “life span.”It is known that self-contained power supplies, such as batteries, havethe ability to recover after some kind of use. For optimization with thepresent invention, the device is constructed within certain parametersthat, for a defined procedure, will perform accordingly but will belimited or unable to continue performance if the time of use extendspast the procedure. Even though the device might recover and possibly beused again in a different procedure, the device is designed to use thepower cells such that they will most likely not be able to perform atthe enhanced level much outside the range of intended single use periodsor outside the range of aggregate use time. With this in mind, a usefullife or clinical life of the power supply or of the device is defined,which life can also be described as an intended use. It is understoodthat this useful/clinical life does not include periods or occurrencesof use during a testing period thereof to make sure that the deviceworks as intended. The life also does not include other times that thedevice is activated outside the intended procedure, i.e., when it is notactivated in accordance with a surgical procedure.

Conventional batteries available in the market are designed to be usedin two ways: (1) provide a significant amount of power for a shortduration (such as in a high-drain digital device like cameras) or (2)provide a small amount of power over a long duration (such as acomputer's clock backup). If either of these operations is not followed,then the battery begins to heat up. If left unchecked, the battery couldheat to a point where the chemicals could cause significant damage, suchas an explosion. As is apparent, battery explosion is to be avoided.These extremes are prevented in conventional batteries with the presenceof the PTC device—a device that is constructed to limit conduction ofthe battery as the battery increases in temperature (i.e., a positivetemperature coefficient of resistance). The PTC device protectsbatteries and/or circuits from overcurrent and overtemperatureconditions. Significantly, the PTC device protects a battery fromexternal short circuits while still allowing the battery to continuefunctioning after the short circuit is removed. Some batteries provideshort-circuit and/or overtemperature protection using a one-time fuse.However, an accidental short-circuit of such a fused battery causes thefuse to open, rendering the battery useless. PTC-protected batterieshave an advantage over fused batteries because they are able toautomatically “reset” when the short circuit is removed, allowing thebattery to resume its normal operation. Understanding characteristics ofthe PTC device is particularly important in the present inventionbecause the motor will be drawing several times greater current thanwould ever be seen in a typical high-drain application.

The PTC device is provided in series with the anode and cathode and ismade of a partially conducting layer sandwiched between two conductivelayers, for example. The device is in a low-resistance condition at atemperature during a normal operation (depending on circuit conditionsin which the device is used, for example, from room temperature to 40°C.). On exposure to high temperature due to, for example, unusuallylarge current resulting from the formation of a short circuit orexcessive discharge (depending on circuit conditions in which the deviceis used, for example, from 60° to 130° C.), the PTC device switches intoan extremely high-resistance mode. Simply put, when a PTC device isincluded in a circuit and an abnormal current passes through thecircuit, the device enters the higher temperature condition and,thereby, switches into the higher resistance condition to decrease thecurrent passing through the circuit to a minimal level and, thus,protect electric elements of the circuit and the battery/ies. At theminimal level (e.g., about 20% of peak current), the battery can cooloff to a “safe” level at which time greater power can be supplied. Thepartially conducting layer of the PTC device is, for example, acomposite of carbon powder and polyolefin plastic. Further descriptionof such devices is unnecessary, as these devices are described and arewell known in the art.

Because PTC circuits of different manufacturers operate with differentcharacteristic behaviors, the present invention takes advantage of thisfeature and provides a process for optimizing the selection of aparticular battery to match a particular motor and a particular use. Anexamination of the time when the PTC device switches to the higherresistance condition can be used as this indicator for optimizing aparticular motor and drive train to a battery. It is desirable to knowwhen the PTC device makes this switch so that, during normal stapleruse, the PTC device does not make this change.

Exemplary batteries were loaded with various levels from approximately 3amps to approximately 8 amps. At the high end, the PTC device changed tothe high-resistance state almost immediately, making this current leveltoo high for standard CR123 cells. It was determined that, for between 4and 6 amps, one manufacturer's cell had PTC activation sooner thananother manufacturer's cell. The longest PTC changeover duration for thesecond manufacturer was >3 minutes for 4 amps, approximately 2 minutesfor 5 amps, and almost 50 seconds for 6 amps. Each of these durationswas significantly greater than the 8-second peak load requirement.Accordingly, it was determined that the second manufacturer's cellswould be optimal for use at peak amps as compared to the firstmanufacturer's cells.

Initially, it was surmised that higher amperes with lower or constantvoltage would generate higher power out of the power cell(s). Based uponthe configuration of 6 cells in series, the peak voltage could be 18volts with a peak current of only 6 amps. Placing cells in parallel, intheory, should allow a higher peak amperage and a 3×2 configuration (twoparallel set of three cells in series) could have a 9 volt peak with upto a 12 amp peak.

Different single cells were investigated and it was confirmed that arelatively low voltage (about 1.5 to 2 volts) and approximately 4 to 6amperes produces the highest power in Watts. Two six-cell configurationswere examined: a 6×1 series connection and a 3×2 parallel connection.The 3×2 configuration produced the greatest peak amperes ofapproximately 10 amps. The 6×1 configuration produced about 6 amps peakand the single cell was able to peak at 5-6 amps before the PTC devicechanged state. This information indicated the state at which any singlecell in the series group would be activating its PTC device and, thus,limiting current through the entire group of cells. Thus, the tentativeconclusion of yielding peak amps at lower voltage with a 3×2configuration was maintained.

Three different CR123 battery configurations were tested: 4×1, 6×1, and3×2, to see how fast the pinion would move the rack (in inches persecond (“IPS”)) for the 120# and 180# loads and for a given typicalgearing. The results of this real world dynamic loading test are shownin the chart of FIG. 30, for both the 120# load:

-   -   the 4×1 battery pack was able to move the load at about 0.6 IPS        at approximately 2.5 amps but at approximately 8 volts;    -   the 6×1 battery pack was able to move the load at about 0.9 IPS        at approximately 2.5 amps but at approximately 13 volts; and    -   the 3×2 battery pack was able to move the load at about 0.4 IPS        at approximately 2.5 amps but at approximately 6 volts;        and the 180# load:    -   the 4×1 battery pack was able to move the load at about 0.65 IPS        at approximately 4 amps but at approximately 7.5 volts;    -   the 6×1 battery pack was able to move the load at about 0.9 IPS        at approximately 4 amps but at approximately 12 volts; and    -   the 3×2 battery pack was able to move the load at about 0.4 IPS        at approximately 4 amps but at approximately 7 volts.        Clearly, the peak current was limited and this limit was        dependent upon the load. This experiment revealed that the motor        drew a similar current regardless of the power supply for a        given load but that the voltage changed depending upon the        battery cell configuration. With respect to either load, the        power output was the greatest in the 6×1 configuration and not        in the 3×2 configuration, as was expected. From this, it was        determined that the total power of the cell pack is driven by        voltage and not by current and, therefore, the parallel        configuration (3×2) was not the path to take in optimizing the        power source.

Traditionally, when designing specifications for a motor, the windingsof the motor are matched to the anticipated voltage at which the motorwill be run. This matching takes into account the duration of individualcycles and the desired overall life of the product. In a case of anelectric stapling device the motor will only be used for very shortcycles and for a very short life, traditional matching methods yieldresults that are below optimal. Manufacturers of the motors give avoltage rating on a motor that corresponds to the number of turns of thewindings. The lower the number of turns, the lower the rated voltage.Within a given size of motor winding, a lower number of turns allowslarger wire to be used, such that a lower number of turns results in alower resistance in the windings, and a higher number of turns resultsin a higher resistance. These characteristics limit the maximum currentthat the motor will draw, which is what creates most of the heat anddamage when the motor is overdriven. For the present invention, adesirable configuration will have the lowest winding resistance to drawthe most current from the power supply (i.e., battery pack). By runningthe motor at a voltage much higher than the motor rating, significantlygreater power can be drawn from similarly sized motors. This trait wasverified with testing of nearly identical coreless motors that onlyvaried in winding resistance (and, hence, the number of turns). Forexample, 12-volt and 6-volt rated motors were run with 6 cells (i.e., at19.2 volts). The motors rated for 12 volts output peak power of 4 Wattswith the battery voltage only falling slightly to 18 volts when drawing0.7 amps. In comparison, the motors rated for 6 volts output 15 Watts ofpower with the voltage dropping to 15 volts but drawing 2 amps ofcurrent. Therefore, the lower resistance windings were selected to drawenough power out of the batteries. It is noted that the motor windingsshould be balanced to the particular battery pack so that, in a stallcondition, the motor does not draw current from the cells sufficient toactivate the PTC, which condition would impermissibly delay use of anelectric surgical stapler during an operation.

The 6×1 power cell configuration appeared to be more than sufficient tomeet the requirements of the electric stapling device. Nonetheless, atthis point, the power cell can be further optimized to determine if sixcells are necessary to perform the required work. Four cells were, then,tested and it was determined that, under the 120# load, the motor/drivetrain could not move the rack over the 60 mm span within 3 seconds. Sixcells were tested and it was determined that, under the 120# load, themotor/drive train could move the rack over the 60 mm span in 2.1seconds—much faster than the 3-second requirement. It was furtherdetermined that, under the 180# load, the motor/drive train could movethe rack over the 60 mm span in less than 2.5 seconds—much quicker thanthe 8-second requirement. At this point, it is desirable to optimize thepower source and mechanical layout to make sure that there is no“runaway” stapling/cutting; in other words, if the load is significantlyless than the required 180# maximum, or even the 120# maximum, then itwould not be desirable to have the rack move too fast.

The gear reduction ratio and the drive system need to be optimized tokeep the motor near peak efficiency during the firing stroke. Thedesired stroke of 60 mm in 3 seconds means a minimum rack velocity of 20mm/sec (˜0.8 inches/second). To reduce the number of variables in theoptimization process, a basic reduction of 333:1 is set in the gear box.This leaves the final reduction to be performed by the gears presentbetween the output shaft 214 of the gear box and the rack 217, whichgears include, for example, a bevel gear 215 and the pinion 216 (whichdrives the rack), a simplified example of which is illustrated in FIG.31.

These variables can be combined into the number of inches of rack travelwith a single revolution of the output shaft 214 of the 333:1 gearbox.If the gearbox output (in rpm) never changed, it would be a simplefunction to match the inches of rack travel per output shaft revolution(“IPR”) to the output rpm to get a desired velocity as follows:

(60 rpm→1 revolution/second (rps); 1 rps @ 0.8 IPR→0.8 in/sec).

In such an idealized case, if the IPR is plotted against velocity, astraight line would be produced. Velocity over a fixed distance can befurther reduced to Firing Time. Thus, a plot of Firing Time versus IPRwould also be a straight line in this idealized case. However, output ofthe motor (in rpm) and, therefore, of the gearbox, is not fixed becausethis speed varies with the load. The degree of load determines theamount of power the motor can put out. As the load increases, the rpmsdecrease and the efficiency changes. Based upon an examination ofefficiency with differing loads, it has been determined that efficiencypeaks at just over 60%. However, the corresponding voltage and amperesat this efficiency peak are not the same as at the point of peak power.Power continues to increase as the load increases until the efficiencyis falling faster than the power is increasing. As the IPR increases, anincrease in velocity is expected, but a corresponding increase in IPRlowers the mechanical advantage and, therefore, increases the load. Thisincreasing load, with the corresponding decrease in efficiency atprogressively higher loads, means that a point will exist when greatervelocity out of the rack is no longer possible with greater IPR. Thisbehavior is reflected as a deviation from a predicted straight line inthe plot of Firing Time (in sec) versus IPR. Experimentation of thesystem of the present invention reveals that the boundary betweenunnecessary mechanical advantage and insufficient mechanical advantageoccurs at approximately 0.4 IPR.

From this IPR value, it is possible to, now, select the final gear ratioof the bevel gear 215 to be approximately three times greater (3:1) thanthe sprocket of the output shaft. This ratio translates into anapproximate IPR of 0.4.

Now that the bevel gear 215 has been optimized, the battery pack can bereexamined to determine if six cells could be reduced to five or evenfour cells, which would save cost and considerably decrease the volumeneeded for the power supply within the handle. A constant load ofapproximately 120# was used with the optimized motor, drive train, bevelgear, and rack and pinion and it was discovered that use of 4 cellsresulted in an almost 5 second time period for moving the rack 60 mm.With 5 cells, the time was reduced to approximately 3.5 seconds. With a6-cell configuration, the time was 2.5 seconds. Thus, interpolating thiscurve resulted in a minimum cell configuration of 5.5 cells. Due to thefact that cells only can be supplied in integer amounts, it wasdiscovered that the 6-cell configuration was needed to meet therequirements provided for the electric stapling device.

From this, the minimum power source volume could be calculated as afixed value, unless different sized cells could be used that providedthe same electrical power characteristics. Lithium cells referred asCR2s have similar electrical power characteristics as have CR123s butare smaller. Therefore, using a 6-cell power supply of CR2s reduced thespace requirement by more than 17%.

As set forth in detail above, the power source (i.e., batteries), drivetrain, and motor are optimized for total efficiency to deliver thedesired output force within the required window of time for completingthe surgical procedure. The efficiency of each kind of power source,drive train, and motor was examined and, thereafter, the type of powersource, drive train, and motor was selected based upon this examinationto deliver the maximum power over the desired time period. In otherwords, the maximum-power condition (voltage and current) is examinedthat can exist for a given period of time without activating the PTC(e.g., approximately 15 seconds). The present invention locates thevoltage-current-power value that optimizes the way in which power isextracted from the cells to drive the motor. Even after suchoptimization, other changes can be made to improve upon the features ofthe electric stapler 1.

Another kind of power supply can be used and is referred to herein as a“hybrid” cell. In such a configuration, a rechargeable Lithium-ion orLithium-polymer cell is connected to one or more of the optimized cellsmentioned above (or perhaps another primary cell of smaller size but ofa similar or higher voltage). In such a configuration, the Li-ion cellwould power the stapling/cutting motor because the total energycontained within one CR2 cell is sufficient to recharge the Li ion cellmany times, however, the primary cells are limited as to delivery.Li-ion and Li-Polymer cells have very low internal resistance and arecapable of very high currents over short durations. To harness thisbeneficial behavior, a primary cell (e.g., CR123, CR2, or another cell)could take 10 to 30 seconds to charge up the secondary cell, which wouldform an additional power source for the motor during firing. Analternative embodiment of the Li-ion cell is the use of a capacitor;however, capacitors are volume inefficient. Even so, a super capacitormay be put into the motor powering system; it may be disconnectedelectrically therefrom until the operator determines that additionalpower is required. At such a time, the operator would connect thecapacitor for an added “boost” of energy.

As mentioned above, if the load on the motor increases past a givenpoint, the efficiency begins to decrease. In such a situation, amulti-ratio transmission can be used to change the delivered power overthe desired time period. When the load becomes too great such thatefficiency decreases, a multi-ratio transmission can be used to switchthe gear ration to return the motor to the higher efficiency point, atwhich, for example, at least a 180# force can be supplied. It is noted,however, that the motor of the present invention needs to operate inboth forward and reverse directions. In the latter operating mode, themotor must be able to disengage the stapling/cutting instrument from outof a “jammed” tissue clamping situation. Thus, it would be beneficialfor the reverse gearing to generate more force than the forward gearing.

With significantly varying loads, e.g., from low pounds up to 180pounds, there is the possibility of the drive assembly being toopowerful in the lower end of the load range. Thus, the invention caninclude a speed-governing device. Possible governing devices includedissipative (active) governors and passive governors. One exemplarypassive governor is a flywheel, such as the energy storage element 56,456 disclosed in U.S. Patent Application No. 2005/0277955 to Palmer etal. Another passive governor that can be used is a “fly” paddlewheel.Such an assembly uses wind resistance to govern speed because it absorbsmore force as it spins faster and, therefore, provides a speed-governingcharacteristic when the motor is moving too fast. Another kind ofgovernor can be a compression spring that the motor compresses slowly toa compressed state. When actuation is desired, the compressed spring isreleased, allowing all of the energy to be transferred to the drive in arelatively short amount of time. A further exemplary governor embodimentcan include a multi-stage switch having stages that are connectedrespectively to various sub-sets of the battery cells. When low force isdesired, a first switch or first part of a switch can be activated toplace only a few of the cells in the power supply circuit. As more poweris desired, the user (or an automated computing device) can placesuccessive additional cells into the power supply circuit. For example,in a 6-cell configuration, the first 4 cells can be connected to thepower supply circuit with a first position of a switch, the fifth cellcan be connected with a second position of the switch, and the sixthcell can be connected with a third position of the switch.

Electric motors and the associated gear box produce a certain amount ofnoise when used. The stapler of the present invention isolates the motorand/or the motor drive train from the handle to decrease both theacoustic and vibration characteristics and, thereby, the overall noiseproduced during operation. In a first embodiment, a dampening materialis disposed between the handle body and both of motor and the drivetrain. The material can be foam, such as latex, polyester, plant-based,polyether, polyetherimide, polyimide, polyolefin, polypropylene,phenolic, polyisocyanates, polyurethane, silicone, vinyl, ethylenecopolymer, expanded polyethylene, fluoropolymer, or styrofoam. Thematerial can be an elastomer, such as silicone, polyurethane,chloroprene, butyl, polybutadiene, neoprene, natural rubber, orisoprene. The foam can be closed cellular, open cellular, flexible,reticular, or syntactic, for example. The material can be placed atgiven positions between the handle and motor/gear box or can entirelyfill the chamber surrounding the motor/gear box. In a second embodiment,the motor and drive train are isolated within a nested boxconfiguration, sometimes referred to as a “Chinese Box” or “Russiannesting doll.” In such a configuration, the dampening material is placedaround the motor/gear box and the two are placed within a first box withthe gear box shaft protruding therefrom. Then, the first box is mountedwithin the “second box”—the handle body—and the dampening material isplace between the first box and the handle interior.

The electric stapler of the present invention can be used in surgicalapplications. Most stapling devices are one-time use. They can bedisposed after one medical procedure because the cost is relatively low.The electric surgical stapler, however, has a greater cost and it may bedesirable to use at least the handle for more than one medicalprocedure. Accordingly, sterilization of the handle components after usebecomes an issue. Sterilization before use is also significant. Becausethe electric stapler includes electronic components that typically donot go through standard sterilization processes (i.e., steam or gammaradiation), the stapler needs to be sterilized by other, possibly moreexpensive, means such as ethylene-oxide gas. It would be desirable,however, to make the stapler available to gamma radiation sterilizationto reduce the cost associated with gas sterilization. It is known thatelectronics are usable in space, which is an environment where suchelectronics are exposed to gamma radiation. In such applications,however, the electronics need to work while being exposed. In contrast,the electric stapler does not need to work while being exposed to thegamma sterilization radiation. When semiconductors are employed, even ifthe power to the electronics is turned off, gamma radiation willadversely affect the stored memory. These components only need towithstand such radiation and, only after exposure ceases, need to beready for use. Knowing this, there are various measures that can betaken to gamma-harden the electronic components within the handle.First, instead of use MOSFET memory, for example, fusable link memoriescan be used. For such memories, once the fuses are programmed (i.e.,burnt), the memory becomes permanent and resistant to the gammasterilization. Second, the memory can be mask-programmed. If the memoryis hard programmed using masks, gamma radiation at the level for medicalsterilization will not adversely affect the programming. Third, thesterilization can be performed while the volatile memory is empty and,after sterilization, the memory can be programmed through variousmeasures, for example, a wireless link including infrared, radio,ultrasound, or Bluetooth communication can be used. Alternatively, oradditionally, external electrodes can be contacted in a cleanenvironment and these conductors can program the memory. Finally, aradiopaque shield (made from molybdenum or tungsten, for example) can beprovided around the gamma radiation sensitive components to preventexposure of these components to the potentially damaging radiation.

As set forth herein, characteristics of the battery, drive train, andmotor are examined and optimized for an electric stapling application.The particular design (i.e., chemistry and PTC) of a battery willdetermine the amount of current that can be supplied and/or the amountof power that can be generated over a period of time. It has beendetermined that standard alkaline cells do not have the ability togenerate the high power needed over the short period of time to effectactuation of the electric stapling device. It was also determined thatsome lithium-manganese dioxide cells also were unable to meet the needsfor actuating the stapling device. Therefore, characteristics of certainlithium-manganese dioxide cell configurations were examined, such as theelectrolyte and the positive temperature coefficient device.

It is understood that conventional lithium-manganese dioxide cells(e.g., CR123 and CR2) are designed for loads over a long period of time.For example, SUREFIRE® markets flashlights and such cells and statesthat the cells will last for from 20 minutes to a few hours (3 to 6) atthe maximum lumen output of the flashlight. Load upon the cells(s)during this period of time is not close to the power capacity of thebattery(ies) and, therefore, the critical current rate of thebattery(ies) is not reached and there is no danger of overheating orexplosion. If such use is not continuous, the batteries can last throughmany cycles (i.e., hundreds) at this same full power output.

Simply put, such batteries are not designed for loads over a period of10 seconds or less, for example, five seconds, and are also not designedfor a small number of uses, for example, ten to fifteen. What thepresent invention does is to configure the power supply, drive train,and motor to optimize the power supply (i.e., battery) for a smallnumber of uses with each use occurring over a period of less than tenseconds and at a load that is significantly higher than rated.

All of the primary lithium cells that were examined possess a criticalcurrent rate defined by the respective PTC device and/or the chemistryand internal construction. If used above the critical current rate for aperiod of time, the cells can overheat and, possibly, explode. Whenexposed to a very high power demand (close to the PTC threshold) with alow number of cycles, the voltage and amperage profiles do not behavethe same as in prior art standard uses. It has been found that somecells have PTC devices that prevent generation of power required by thestapler of the present invention, but that other cells are able togenerate the desired power (can supply the current and voltage) forpowering the electric stapling device. This means that the criticalcurrent rate is different depending upon the particular chemistry,construction, and/or PTC of the cell.

The present invention configures the power supply to operate in a rangeabove the critical current rate, referred to herein as the“Super-Critical Current Rate.” It is noted within the definition ofSuper-Critical Current Rate also is an averaging of a modulated currentsupplied by the power supply that is above the critical current rate.Because the cells cannot last long while supplying power at theSuper-Critical Current Rate, the time period of their use is shortened.This shortened time period where the cells are able to operate at theSuper-Critical Current Rate is referred to herein as the “Super-CriticalPulse Discharge Period,” whereas the entire time when the power supplyis activated is referred to as a “Pulse Discharge Period.” In otherwords, the Super-Critical Pulse Discharge Period is a time that is lessthan or equal to the Pulse Discharge Period, during which time thecurrent rate is greater than the critical current rate of the cells. TheSuper-Critical Pulse Discharge Period for the present invention is lessthan about 16 seconds, in other words, in a range of about one-half tofifteen seconds, for example, between two and four seconds and, moreparticularly, at about three seconds. During the life of the staplingdevice, the power supply may be subjected to the Super-Critical CurrentRate over the Pulse Discharge Period for at least one time and less thantwenty times within the time of a clinical procedure, for example,between approximately five and fifteen times, in particular, between tenand fifteen times within a period of five minutes. Therefore, incomparison to the hours of use for standard applications of the powersupply, the present invention will have an aggregate use, referred to asthe Aggregate Pulse Time, of, at most, approximately 200 to 300 seconds,in particular, approximately 225 seconds. It is noted that, during anactivation, the device may not be required to exceed or to always exceedthe Super-Critical Current Rate in a given procedure because the loadpresented to the instrument is dependent upon the specific clinicalapplication (i.e., some tissue is denser than others and increasedtissue density will increase load presented to device). However, thestapler is designed to be able to exceed the Super-Critical Current Ratefor a number of times during the intended use of the surgical procedure.Acting in this Super-Critical Pulse Discharge Period, the device canoperate a sufficient amount of times to complete the desired surgicalprocedure, but not many more because the power supply is asked toperform at an increased current.

When performing in the increased range, the force generated by thedevice, e.g., the electric stapler 1, is significantly greater thanexisted in a hand-powered stapler. In fact, the force is so much greaterthat it could damage the stapler itself. In one exemplary use, the motorand drive assemblies can be operated to the detriment of the knife bladelock-out feature—the safety that prevents the knife blade 1060 fromadvancing when there is no staple cartridge or a previously fired staplecartridge in the staple cartridge holder 1030. This feature isillustrated in FIG. 32. As discussed, the knife blade 1060 should beallowed to move distally only when the staple sled 102 is present at thefiring-ready position, i.e., when the sled 102 is in the positionillustrated in FIG. 32. If the sled 102 is not present in this position,this can mean one of two things, either there is no staple cartridge inthe holder 1030 or the sled 102 has already been moved distally—in otherwords, a partial or full firing has already occurred with the loadedstaple cartridge. Thus, the blade 1060 should not be allowed to move, orshould be restricted in its movement. Accordingly, to insure that thesled 102 can prop up the blade 1060 when in a firing state, the sled 102is provided with a lock-out contact surface 104 and the blade 1060 isprovided with a correspondingly shaped contact nose 1069. It is noted atthis point that, the lower guide wings 1065 do not rest against a floor1034 in the cartridge holder 1030 until the blade 1060 has moveddistally past an edge 1035. With such a configuration, if the sled 102is not present at the distal end of the blade 1060 to prop up the nose1069, then the lower guide wings 1065 will follow the depression 1037just proximal of the edge 1035 and, instead of advancing on the floor1034, will hit the edge 1035 and prevent further forward movement of theblade 1060. To assist with such contact when the sled 102 is not present(referred to as a “lock out”), the staple cartridge 1030 has a platespring 1090 (attached thereto by at least one rivet 1036) for biasingthe blade 1060. With the plate spring 1090 flexed upward and pressingdownward against the flange 1067 (at least until the flange 1067 isdistal of the distal end of the plate spring 1090), a downwardlydirected force is imparted against the blade 1060 to press the wings1065 down into the depression 1037. Thus, as the blade 1060 advancesdistally without the sled 102 being present, the wings 1065 follow thelower curve of the depression 1037 and are stopped from further distalmovement when the distal edge of the wings 1065 hit the edge 1035.

This safety feature operates as described so long as the forcetransmitted by the knife blades 1062 to the blade 1060 is not greatenough to tear off the lower guide wings 1065 from the blade 1060. Withthe forces able to be generated by the power supply, motor and drivetrain of the present invention, the blade 1060 can be pushed distally sostrongly that the wings 1065 are torn away. If this occurs, there is noway to prevent distal movement of the blade 1060 or the sled 102.Accordingly, the present invention provides a way to lower the forcesable to be imparted upon the wings 1065 prior to their passage past theedge 1035. In other words, the upper limit of force able to be appliedto the blade 1060 is reduced in the first part of blade travel (past theedge 1035) and increases after the wings 1065 have cleared the edge 1035and rest on the floor 1034. More specifically, a first exemplaryembodiment of this two-part force generation limiter takes the form of acircuit in which only one or a few of the cells in the power supply areconnected to the motor during the first part of the stapling/cuttingstroke and, in the second part of the stapling/cutting stroke, most orall of the cells in the power supply are connected to the motor. Anexemplary form of such a circuit is illustrated in FIG. 33. In thisembodiment, when the switch 1100 is in the “A” position, the motor(e.g., stapling motor 210) is only powered with one power cell 602 (of apossible four in this exemplary embodiment). However, when the switch1100 is in the “B” position, the motor is powered with all four of thecells 602 of the power supply 600, thereby increasing the amount offorce that can be supplied to the blade 1060. Control of the switch 1100between the A and B positions can occur by positioning a second switchsomewhere along the blade control assembly or along the sled 102, thesecond switch sending a signal to a controller after the wings 1065 havepassed the edge 1035. It is noted that this embodiment of the controlcircuit is only exemplary and any similarly performing assembly canprovide the lock-out protection for the device.

An exemplary form of a forward and reverse motor control circuit isillustrated in FIG. 34. This exemplary embodiment uses a double-throw,double pole switch 1200. The switch 1200 is normally spring-biased to acenter position in which both poles are off. The motor M illustratedcan, for example, represent the stapling motor 210 of the presentinvention. As can be seen, the power-on switch 1210 must be closed toturn on the device. Of course, this switch is optional. When a forwardmovement of the motor M is desired, the switch 1200 is placed in theright position as viewed in FIG. 34, in which power is supplied to themotor to run the motor in a first direction, defined as the forwarddirection here because the “+” of the battery is connected to the “+” ofthe motor M. In this forward switching position, the motor M can powerthe blade 1060 in a distal direction. Placement of an appropriate sensoror switch to indicate the forward-most desired position of the blade1060 or the sled 102 can be used to control a forward travel limitswitch 1220 that interrupts power supply to the motor M and preventsfurther forward travel, at least as long as the forward travel limitswitch 1220 remains open. Circuitry can be programmed to never allow theforward travel limit switch 1220 to close and complete the circuit or toonly allow resetting of the forward travel limit switch 1220 when a newstaple cartridge, for example, is loaded.

When a reverse movement of the motor M is desired, the switch 1200 isplaced in the left position as viewed in FIG. 34, in which power issupplied to the motor to run the motor in a second direction, defined asthe reverse direction here because the “−” of the battery is connectedto the “+” of the motor M. In this reverse switching position, the motorM can power the blade 1060 in a proximal direction. Placement of anappropriate sensor or switch to indicate the rearward-most desiredposition of the blade 1060 or the sled 102 can be used to control arearward travel limit switch 1230 that interrupts power supply to themotor M and prevents further rearward travel, at least as long as therearward travel limit switch 1230 remains open. It is noted that otherswitches (indicated with dotted arrows) can be provided in the circuitto selectively prevent movement in either direction independent of thelimit switches 1220, 1230.

It is noted that the motor can power the gear train with a significantamount of force, which translates into a high rotational inertia. Assuch, when any switch mentioned with respect to FIGS. 33 and 34 is usedto turn off the motor, the gears may not just stop. Instead, therotational inertia continues to propel, for example, the rack 217 in thedirection it was traveling when power to the motor was terminated. Suchmovement can be disadvantageous for many reasons. By configuring thepower supply and motor appropriately, a circuit can be formed tosubstantially eliminate such post-termination movement, thereby givingthe user more control over actuation.

FIG. 35 illustrates an exemplary embodiment where the motor (forexample, stapling motor 210) is arrested from further rotation whenforward or reverse control is terminated. FIG. 35 also illustratesalternative embodiments of the forward/reverse control and of themulti-stage power supply. The circuit of FIG. 35 has a motor arrestsub-circuit utilizing a short-circuit property of an electrical motor.More specifically, the electrical motor M is placed into a short-circuitso that an electrically generated magnetic field is created inopposition to the permanent magnetic field, thus slowing thestill-spinning motor at a rate that substantially preventsinertia-induced over-stroke. To explain how the circuit of FIG. 35 canbrake the motor M, an explanation of the forward/reverse switch 1300 isprovided. As can be seen, the forward/reverse switch 1300 has threepositions, just like the switch 1200 of FIG. 34. When placed in theright position, the motor M is actuated in a forward rotation direction.When placed in the left position, the motor M is actuated in a rearwardrotation direction. When the forward/reverse switch 1300 is notactuated—as shown in FIG. 35—the motor M is short-circuited. This shortcircuit is diagrammatically illustrated by the upper portion of theforward/reverse switch 1300. It is noted that the switching processes ina braking switch is desired to take place in a time-delayed manner,which is also referred to as a break-before-make switchingconfiguration. When switching over from operating the motor M to brakingthe motor M, the double-pole, double throw portion of theforward/reverse switch 1300 is opened before the motor short circuit iseffected. Conversely, when switching over from braking the motor M tooperating the motor M, the short circuit is opened before theforward/reverse switch 1300 can cause motor actuation. Therefore, inoperation, when the user releases the 3-way switch 1300 from either theforward or reverse positions, the motor M is short-circuited and brakesquickly.

Other features of the circuit in FIG. 35 have been explained with regardto FIG. 34. For example, an on/off switch 1210 is provided. Also presentis the power lock-out switch 1100 that only powers the motor with onepower cell 602′ in a given portion of the actuation (which can occur atthe beginning or at any other desired part of the stroke) and powers themotor M with all of the power cells 602 (here, for example, six powercells) in another portion of the actuation.

A new feature of the reverse and forward limit switches 1320, 1330prevents any further forward movement of the motor M after the forwardlimit switch 1320, 1330 is actuated. When this limit is reached, theforward limit switch 1330 is actuated and the switch moves to the secondposition. In this state, no power can get to the motor for forwardmovement but power can be delivered to the motor for reverse movement.The forward limit switch can be programmed to toggle or be a one-timeuse for a given staple cartridge. More specifically, the forward limitswitch 1330 will remain in the second position until a reset occurs byreplacing the staple cartridge with a new one. Thus, until thereplacement occurs, the motor M can only be powered in the reversedirection. If the switch is merely a toggle, then power can be restoredfor additional further movement only when the movement has retreated thepart away from actuating the forward limit switch 1330.

The reverse limit switch 1320 can be configured similarly. When thereverse limit is reached, the reverse limit switch 1320 moves to thesecond position and stays there until a reset occurs. It is noted that,in this position, the motor M is in a short-circuit, which preventsmotor movement in either direction. With such a configuration, theoperation of the stapler can be limited to a single stroke up to theforward limit and a single retreat up to the rear limit. When both haveoccurred, the motor M is disabled until the two limit switches 1320,1330 are reset.

The foregoing description and accompanying drawings illustrate theprinciples, preferred embodiments and modes of operation of theinvention. More specifically, the optimized power supply, motor, anddrive train according to the present invention has been described withrespect to a surgical stapler. However, the invention should not beconstrued as being limited to the particular embodiments discussedabove. Additional variations of the embodiments discussed above will beappreciated by those skilled in the art as well as for applications,unrelated to surgical devices, that require an advanced power or currentoutput for short and limited durations with a power cell having alimited power or current output. As is shown and described, whenoptimized according to the present invention, a limited power supply canproduce lifting, pushing, pulling, dragging, retaining, and other kindsof forces sufficient to move a substantial amount of weight, forexample, over 82 kg.

The above-described embodiments should be regarded as illustrativerather than restrictive. Accordingly, it should be appreciated thatvariations to those embodiments can be made by those skilled in the artwithout departing from the scope of the invention as defined by thefollowing claims.

What is claimed is:
 1. A surgical instrument, comprising: atissue-compressing device comprising opposing compression surfaces; aswitching element having first and second switching states changedsolely by mechanical movements; and a biasing element mechanicallycoupled to the switching element, the biasing element retaining theswitching element in one of the first and second switching states untila pre-determined force is imparted to the switching element, wherein:the pre-determined force is an amount of force proportional to anoptimal tissue compression force of compressed tissue disposed betweenthe opposing compression surfaces; and the switching element ispositioned in line with the tissue-compressing device to cause a force,proportional to a force placed upon compressed tissue disposed betweenthe opposing compression surfaces, to be imparted to the switchingelement.
 2. The surgical instrument according to claim 1, wherein theswitching element is a mechanical binary-output electrical switch. 3.The surgical instrument according to claim 2, wherein the firstswitching state is an open electrical state and the second switchingstate is a closed electrical state.
 4. The surgical instrument accordingto claim 1, wherein the biasing element is adjustable.
 5. The surgicalinstrument according to claim 4, wherein the pre-determined force of thebiasing element is set to an amount proportional to the optimal tissuecompression force of the compressed tissue.
 6. The surgical instrumentaccording to claim 1, wherein the switching element is positioned tocause substantially the same force placed upon the compressed tissuedisposed between the opposing compression surfaces to be placed upon theswitching element.
 7. The surgical instrument according to claim 5,wherein setting the pre-determined force to an amount proportional tothe optimal tissue compression force of the compressed tissue causes achange of the switching state to occur when a compression force placedon tissue by the opposing compression surfaces of the tissue-compressingdevice is at least as great as the optimal tissue compression force. 8.The surgical instrument according to claim 1, wherein: thetissue-compressing device has a compression axis; and the switchingelement comprises an actuation gap oriented to span along thecompression axis and to cause a change of the switching state dependentupon a force expanding along the compression axis.
 9. The surgicalinstrument according to claim 1, wherein the tissue-compressing devicecomprises an end effector with two opposing jaws that compress tissuedisposed therebetween.
 10. A surgical instrument, comprising: atissue-compressing device comprising opposing compression surfaces; aswitching element having first and second switching states changedsolely by mechanical movements; and a biasing element mechanicallycoupled to the switching element, the biasing element imparting apre-determined force on the switching element to retain the switchingelement in one of the first and second switching states until aswitching force at least as great as the pre-determined force imposed bythe biasing element is imparted to the switching element and causes achange of the switching state to occur, wherein: the pre-determinedforce is an amount of force proportional to an optimal tissuecompression force of the compressed tissue disposed between the opposingcompression surfaces; and the switching element is positioned in linewith the tissue-compressing device to cause the switching force,proportional to the force placed upon compressed tissue disposed betweenthe opposing compression surfaces, to be imparted to the switchingelement.
 11. The surgical instrument according to claim 10, wherein theswitching element is a mechanical binary-output electrical switch. 12.The surgical instrument according to claim 11, wherein the firstswitching state is an open electrical state and the second switchingstate is a closed electrical state.
 13. The surgical instrumentaccording to claim 10, wherein the biasing element is adjustable. 14.The surgical instrument according to claim 13, wherein thepre-determined force of the biasing element is set to an amountproportional to the optimal tissue compression force of the compressedtissue.
 15. The surgical instrument according to claim 10, wherein theswitching element is positioned to cause substantially the same forceplaced upon the compressed tissue disposed between the opposingcompression surfaces to be placed upon the switching element.
 16. Thesurgical instrument according to claim 14, wherein setting of thepre-determined force to an amount proportional to the optimal tissuecompression force of the compressed tissue causes a change of theswitching state to occur when a compression force placed on tissue bythe opposing compression surfaces of the tissue-compressing device is atleast as great as the optimal tissue compression force.
 17. The surgicalinstrument according to claim 10, wherein: the tissue-compressing devicehas a compression axis; and the switching element comprises an actuationgap oriented to span along the compression axis and to cause a change ofthe switching state dependent upon a force expanding along thecompression axis.
 18. The surgical instrument according to claim 10,wherein the tissue-compressing device comprises an end effector with twoopposing jaws that compress tissue disposed therebetween.